Improve README of exercise-grids

exercises/exercise-grids/README.md

 # Exercise Grids (DuMuX course)
-The aim of this exercise is to show how to use and adapt different grid implementations in _DuMu<sup>x</sup>_. The DUNE core module dune-grid provides `YaspGrid`, `OneDGrid`, and the meta-grid manager `GeometryGrid`.
+The aim of this exercise is to show how to use and adapt different grid implementations in _DuMu<sup>x</sup>_. The DUNE core module dune-grid provides `Dune::YaspGrid`, `Dune::OneDGrid`, and the meta-grid manager `Dune::GeometryGrid`.
 
 Further grid implementations are available as additional modules. For a summary of the grid types that you can use in _DuMu<sup>x</sup>_, you can have a look at the [grid types overview](
 #overview-of-dune-grid-types-selection) at the end of this exercise.
@@ -53,7 +53,7 @@ template<class TypeTag>
 struct Grid<TypeTag, TTag::Injection2p> { using type = Dune::YaspGrid<2>; };
 ```
 
-This sets the Grid, which belongs to the `Injection2p` type tag, and calls the manager with a basic `YaspGrid` in the second dimension.
+This sets the Grid, which belongs to the `Injection2p` type tag, and calls the manager with a basic `Dune::YaspGrid` in the second dimension.
 
 If we look in the grid manager header file, `dumux/dumux/io/grid/gridmanager_yasp.hh`,
 we will see that there are a few grid development options. Until now, we have used the most basic definition.
@@ -142,8 +142,8 @@ DuMu$^\mathsf{X}$ can also read in grids from external files. There are two supp
 * __`.msh`__ grids are made from the open-source Gmsh software, and is also supported by dumux.
 (see: [Gmsh](http://gmsh.info//) and [Gmsh reference manual](http://gmsh.info//doc/texinfo/gmsh.html))
 
-We can read in simple `.dgf` files using basic YaspGrids, but if we want to use more complicated external grids, we would need to use other grid formats, like `UGGrid` or `ALUGrid`.
-For this example, we can rewrite our Grid Properties to develop an `ALUGrid`. The grid manager class (see `dumux/dumux/io/grid/gridmanager_alu.hh`) takes the following form:
+We can read in simple `.dgf` files using basic YaspGrids, but if we want to use more complicated external grids, we would need to use other grid formats, like `Dune::UGGrid` or `Dune::ALUGrid`.
+For this example, we can rewrite our Grid Properties to develop an `Dune::ALUGrid`. The grid manager class (see `dumux/dumux/io/grid/gridmanager_alu.hh`) takes the following form:
 ```c++
 GridManager<Dune::ALUGrid<dim, dimworld, elType, refinementType>>
 ```
@@ -168,23 +168,23 @@ This grid is made up of triangles (simplices of dimension 2). This element type
 # Overview of DUNE Grid Types (selection)
 
 ## The dune-grid Core Module
-The dune-grid module contains the implementations of `OneDGrid`, `YaspGrid` and `GeometryGrid`.
+The dune-grid module contains the implementations of `Dune::OneDGrid`, `Dune::YaspGrid` and `Dune::GeometryGrid`.
 
-`OneDGrid` and `YaspGrid` are native DUNE grid implementations. OneDGrid provides an unstructured and adaptive one-dimensional grid whereas YaspGrid is a structured, parallel grid. Elements of that grid can be instantiated with uniform sizes or with a spatial grading. Its domain is a d-dimensional hypercube in \(\mathbb{R}^d\), with axis-aligned d-dimensional hypercubes as elements.
+`Dune::OneDGrid` and `Dune::YaspGrid` are native DUNE grid implementations. OneDGrid provides an unstructured and adaptive one-dimensional grid whereas YaspGrid is a structured, parallel grid. Elements of that grid can be instantiated with uniform sizes or with a spatial grading. Its domain is a d-dimensional hypercube in \(\mathbb{R}^d\), with axis-aligned d-dimensional hypercubes as elements.
 
-`GeometryGrid` is a meta grid manager. That means it wraps any other grid implementation ("host grid") and transforms the geometry of that host grid using a user-provided coordinate transformation.
+`Dune::GeometryGrid` is a meta grid manager. That means it wraps any other grid implementation ("host grid") and transforms the geometry of that host grid using a user-provided coordinate transformation.
 
 For more information, see:<br>
-DUNE — The Distributed and Unified Numerics Environment https://doi.org/10.1007/978-3-030-59702-3
+[DUNE — The Distributed and Unified Numerics Environment](https://doi.org/10.1007/978-3-030-59702-3)
 
 ## dune-alugrid
-`ALUGrid` offers cube grids and unstructured simplices. The grids can be two- or three-dimensional. Two-dimensional grids can be embedded into a three-dimensional world space if the represented domain is a manifold.
+`Dune::ALUGrid` offers cube grids and unstructured simplices. The grids can be two- or three-dimensional. Two-dimensional grids can be embedded into a three-dimensional world space if the represented domain is a manifold.
 
 It is a powerful grid for large distributed problems and provides different load-balancing algorithms. 
 
 For more information, see:<br>
-DUNE — The Distributed and Unified Numerics Environment https://doi.org/10.1007/978-3-030-59702-3<br>
-The DUNE-ALUGrid Module https://doi.org/10.11588/ans.2016.1.23252
+[DUNE — The Distributed and Unified Numerics Environment](https://doi.org/10.1007/978-3-030-59702-3)<br>
+[The DUNE-ALUGrid Module](https://doi.org/10.11588/ans.2016.1.23252)
 
 ## dune-foamgrid
 This module is used for one- or two-dimensional grids embedded in a space of arbitrary dimensions. The grids are not required to have a manifold structure, meaning a facet may be shared by more than two elements.
@@ -194,13 +194,12 @@ The geometry approximation for curved domains can be improved by using element p
 It can for example be used to model foams, discrete fractures or network flow problems.
 
 For more information, see:<br>
-The Dune FoamGrid implementation for surface and network grids https://doi.org/10.11588/ans.2017.1.28490
+[The Dune FoamGrid implementation for surface and network grids](https://doi.org/10.11588/ans.2017.1.28490)
 
 ## dune-uggrid
-`UGGrid` supports unstructured grids in both 2D and 3D. 2D grids can contain triangles and quadrilaterals, while 3D grids can include tetrahedra, hexahedra, prisms, and pyramids. Different element types can be combined in one grid. The grid dimension is a template parameter of the `UGGrid` class. Multiple `UGGrid` instances can coexist as long as memory allows. `UGGrid` supports adaptive red-green refinement and non-conforming refinement, as well as anisotropic refinement.
+`Dune::UGGrid` supports unstructured grids in both 2D and 3D. 2D grids can contain triangles and quadrilaterals, while 3D grids can include tetrahedra, hexahedra, prisms, and pyramids. Different element types can be combined in one grid. The grid dimension is a template parameter of the `Dune::UGGrid` class. Multiple instances of that class can coexist as long as memory allows. `Dune::UGGrid` supports adaptive red-green refinement and non-conforming refinement, as well as anisotropic refinement.
 
-For more information, see:<br>
-https://www.dune-project.org/modules/dune-uggrid/
+For more information, see the [Dune website](https://www.dune-project.org/modules/dune-uggrid/).
 
 ## Further Grid Modules
-This section should have given you an overview of the grid implementations that come with the core DUNE installation as well as some additional, regularly-used grid modules. More grid modules are presented on https://dune-project.org/groups/grid/.
+This section should have given you an overview of the grid implementations that come with the core DUNE installation as well as some additional, regularly-used grid modules. More grid modules are presented on the [Dune website](https://dune-project.org/groups/grid/).