[doc][slides] add md-file for runtimeparams-grids

slides/index.md

 ---
 title: DuMuX Course Slides
 ---
-
 - [Introduction to DuMu^x^](./intro.html)
+- [Runtime Parameters and Grids](./runtimeparams-grids.html)
 - [Property System](./properties.html)
 - [Model](./model.html)
 - [Introduction to Multidomain](./multidomain.html)

slides/runtimeparams-grids.md

+---
+title: Runtime Parameters and Grids
+subtitle: Introduction to DuMu$^\mathsf{X}$
+---
+
+# Runtime Parameters
+
+## Runtime Parameters
+
+* Avoid recompiling
+* The same executable can be used to test different sets of parameters via shell script.
+
+<p style="text-align: left;">Practical concern:</p>
+
+* If the parameter can be set at compile time, it is often cleaner and faster to do so. Only use parameters, when it is needed.
+
+## Input-file contents
+
+* Input file syntax:
+  ```ini
+  [MyGroup]
+  MyParameter = 2
+  ```
+* Examples:
+
+  | Groups    | Parameters    |               |            |
+  |-----------|---------------|---------------|------------|
+  | Component | GasDensity    | LiquidDensity | MolarMass  |
+  | Problem   | EnableGravity | Name          |            |
+  | Grid      | Cells         | LowerLeft     | UpperRight |
+
+## Reading Runtime Parameters
+
+* Use runtime parameters in any file in DuMu$^\mathsf{X}$
+  ```cpp
+  paramname_ = getParam<TYPE>(“GROUPNAME.PARAMNAME”);
+  ```
+  or
+  ```cpp
+  paramname_ = getParamFromGroup<TYPE>("GROUPNAME", "PARAMNAME");
+  ```
+* You can also set a default value when calling a runtime parameter. In case that no parameter is set at runtime, the default value will be used. Be careful! Many parameters already have a default value.
+  ```cpp
+  paramname_ = getParam<TYPE>(“GROUPNAME.PARAMNAME”, default);
+  ```
+
+## Reading Runtime Parameters
+
+* Remark: If you need to read in a parameter multiple times in for one problem, use `static const` to reduce runtime. E.g.
+  ```cpp
+  static const bool enableGravity = getParam<bool>("Problem.EnableGravity");
+  ```
+
+## Functions hasParam and hasParamInGroup
+
+* Check: Parameter in input file?
+  ```cpp
+  if (hasParam("GROUPNAME.PARAMNAME"))
+    std::cout << "GROUPNAME.PARAMNAME is read from the input file." << std::endl;
+  else
+    std::cout << "Using the default value for 	GROUPNAME.PARAMNAME." << std::endl;
+  ```
+* Another way of writing the upper
+  ```cpp
+  if (hasParamInGroup("GROUPNAME","PARAMNAME"))
+  ```
+  instead of
+  ```cpp
+  if (hasParam("GROUPNAME.PARAMNAME"))
+  ```
+
+## Parameter list
+
+An overview of all available parameters can be found in the [doxygen documentation](https://dumux.org/docs/doxygen/releases/3.6/a00008.html).
+
+<img src=img/parameterlist.png>
+
+# Grids
+
+## Grid types
+
+* **YASPGrid** (structured, n-dimensional, parallel tensorproduct grid)
+* **UGGrid** (2D/3D, unstructured, parallel, multi-geometry)
+* **ALUGrid** (2D/3D, unstructured, parallel, simplex/cube)
+* **FOAMGrid** (1D-2D, Dynamic, Multi-dimension/Network Problems)
+* **OPMGrid** (Cornerpoint grids)
+
+## Create grid
+
+* Set grid types in properties file:
+  ```cpp
+  // Set the grid type
+  template<class TypeTag>
+  struct Grid<TypeTag, TTag::Injection2p>{
+    using type = Dune::YaspGrid<2>;
+  };
+  ```
+
+* Include the matching grid manager header files in main file.
+  ```cpp
+  // grid manager for yasp grid
+  #include <dumux/io/grid/gridmanager_yasp.hh>
+  ```
+
+* Create grid in the main file
+  ```cpp
+  // try to create a grid (from a grid file or the input file)
+  GridManager<GetPropType<TypeTag, Properties::Grid>> gridManager;
+  gridManager.init();
+  ```
+
+## Grid from file
+
+* Read in grid from file (specified in input-file)
+  ```ini
+  [Grid]
+  File = ./grids/heterogeneousSmall.dgf
+         # relative path to the grid file
+  ```
+
+* Supported grid file formats
+  * DGF (Dune grid format)
+  * Gmsh (gmsh.info)
+  * Cornerpoint grid format (.grdecl file, see opm)
+
+
+## Grid from input
+* Develop grid from basic spatial descriptions (specified in input-file)
+  ```ini
+  [Grid]
+  LowerLeft = 0 0 # x, y entry (3 entries for 3D)
+  UpperRight = 1 1
+  Cells = 10 5
+  ```
+
+<img src=img/params_grid.png width="300">
+
+# Excercises
+## Exercises
+<p style="text-align: left;">Exercise about runtime parameters:</p>
+
+* Go to [https://git.iws.uni-stuttgart.de/dumux-repositories/dumux-course/tree/master/exercises/exercise-runtimeparams](https://git.iws.uni-stuttgart.de/dumux-repositories/dumux-course/tree/master/exercises/exercise-runtimeparams) and check out the README
+
+<p style="text-align: left;">Exercise about grids:</p>
+
+* Go to [https://git.iws.uni-stuttgart.de/dumux-repositories/dumux-course/tree/master/exercises/exercise-grids](https://git.iws.uni-stuttgart.de/dumux-repositories/dumux-course/tree/master/exercises/exercise-grids) and check out the README