Michael Kuron authored Dec 28, 2020 and Markus Holzer committed Dec 28, 2020

Some optional components use Boost MultiArray and PropertyTree, so we still include the headers if available.
We also still search std::experimental for any, filesystem and optional because some otherwise C++17-compliant compilers did not support them in std until recently.

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

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)

This option is OFF by default.
If turned on cmake will notify if a target cannot be build due to a missing module.

- information from CMake to codegen: double/float, OpenMP, ...

External apllications which did not set the C++ standard to 14 in their CMakeLists.txt failed to build. This change allows them to build without further user actions.

- one python file can now generate multiple source files

- Add generator files to targets to show them in VS solutions
- mark generated files as such in CMake

If you have access to the old closed source waLBerla repository, you may restore the complete history with the following command
git fetch git@i10git.cs.fau.de:software/walberla.git 'refs/replace/*:refs/replace/*'