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)

Adding Gnuplot writer for vector field.

Refactoring the Dirichlet and the Neumann boundary conditions.

Scripts tnl-compile and tnl-link were added.

Min. interations feature was fixed in the GMRES method.
Timers for explicit and semi-implicit timestepping were added.

Added: hamilton-jacobi solver, godunov & upwind operators, tnlNeumannBoundaryReflectionCondition, several testing functions.