[2pncmin] beautification, new reference solution, changed to scalar permeability as setup is isotropic

Kilian Weishaupt authored 7 years ago and Timo Koch committed 7 years ago

* fvGeometry, fluxVar and volVar caching
* compare against solution with caching off

In case one dimension is very small take the maximum between the to be tested box dimensions
in the corresponding axis direction. There is one corner case left where the epsilon is very small:
If there are two bboxes of lines, both parallel in an axis direction, their collision is only
detected if the coordinates are an exact match. However, we currently do not see any used case
where this might occur.

Mpfa contributed by DennisGlaeser

This patch reduces dependencies and makes usage of linear solvers more flexible, i.e. for two problems with different typetag

* Linear solvers don't need type tag anymore, in fact they don't need any template params
* the preconditioner block size is now provided for the solve method (see e.g. staggered newton controller)
* the amg has a convencience alias using a TypeTag but is "independent" through indirection via the traits

In case of global caching, the grid variables have to be updated
as otherwise the old solution is written to disk.

* [test][richards] Fix solver include
  (Used to compile before due to indirect include over newtoncontroller.

* make output more clear

* calculate the mass and volume fluxes over two different planes

Use the `DUNE_VERSION*` macros to distinguish between Dune >= 2.6
and < 2.6. Employ the correspondingly correct types, constructors
and function calls for Mappers and ReferenceElements.