use cuda as a first level language in CMake with `enable_language(CUDA)`
enable tests where cuda and codegen are both activated
various minor fixes

Please use mocks for these kind of tests.
a) deterministic
b) faster

for bulk modes, shear modes, even ghost modes, odd ghost modes

This new function does the actual generation using pystencils and creates a target library that can be used as a dependency as usual. One should not list the python script itself anymore in add_executable.
Convention: Use the AppName as a prefix for the generated lib!

Example Usage:

waLBerla_generate_target_from_python( NAME AppNameGeneratedLib FILE GenerateKernel.py OUT_FILES Kernel.h Kernel.cpp)

waLBerla_add_executable ( NAME AppNameGeneratedLibTest DEPENDS GeneratedLib)

To remove code duplication the distinction is now moved
into the generator. Default kernels are "with shape".

Added hydrodynamic force notifications, introduced them to tests and benchmarks, minor documentation and include fixes

ForceTorqueNotification
HeatFluxNotification

- added ability to create custom modules

-fixed relative error calculation
-fixed wrong size of linked cells

Added lbm-mesa_pd coupling to have a fluid-particle coupling to the new rigid particle dynamics simulations

To break unneeded dependencies in postprocessing the SQLite part is
moved to its own module and namespace.
Therefore in the include and the function calls
"postprocessing" hast to be removed or replaced by "sqlite" e.g.:
#include "postprocessing/sqlite/SQLite.h" ->
#include "sqlite/SQLite.h"

postprocessing::store... -> sqlite::store...