Implements cumulant phase field function and a passive incompressible momentum equation. The phase field is only coupled to the fluid velocity but there is no featback to the fluid. Only as a starting step for further developments.

Fix various msvc compiler warnings. With msvc the compiler flags are explicit passed to nvcc with -Xcompiler.

 - metis: do not pass -O3 flag on msvc compiler, as this flag is ignored anyway. Instead of /w pass w0, which is equivalent to /w.
 - RheologyK17LBMKernel: A and B are also defined in D3Q27System.h. Therefore to not hide this declaration they are renamed to A_ and B_
 - additional small clean ups...

Remove debugging ls. Activate double accuracy for the numerical tests. Deactivate 256 & 512 grid sizes.

Add gpu options to root cmake. Add the cmake option for passing the path to the numerial tests. Add git clone test to the CI.