double works, not tested for other types.

Refactoring

See merge request mmg/tnl-dev!3

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)

Content moved to src/Python/__init__.py.in

RAII is a thing :-P

New tests are in src/UnitTests/Containers/

New tests are in src/UnitTests/Containers/Multimaps/

The Host class was combining too many things...

It actually does not affect anything...

Why do problems have this method anyway? It was obviously never used...

When type traits for the "double-float" or "double-double" types are
needed, they should be added as specializations of the
std::numeric_limits template in some of the TNL header files.

There were 2 problems:

- it does not belong into a numerical library
- the approach with hardcoded escape codes is not portable even on Linux

There are separate libraries which solve both of these issues much more
nicely, they should be used instead.

It is not used in current code, it was used only in some legacy benchmarks.