Add StaticVectorFor - for cycle doing all combinations of directions

Heavy Refactorization of DistributedGrids:
	-> Reordered Directions
	-> Add some useless Direction helper functions
	-> Set Up DistributedGrid_Base - shared base with dim template parameter
	-> Add support for communicationGroup created for DistributedGrid (MPI communicator support)

Conflicts:
	src/TNL/Communicators/MpiCommunicator.h

Preapare Distributed Grids for Communication groups (aka MPI Communicator)

Fix DistributedGrid_Base - add missing getEntitiesCount - providing global grid entity count - used in tnl-lbm