Add a preprocessor variable to define the supposed maximum number of groups adjacent to a given group.

Change of the return values in grpsplit_pmmg.c file to be consistant with the other functions. 0 : failure ; 1 : success ; -1 : strong failure
Error handling in libparmmg1.c

Do not retrun immediately in grpSplit if we don't have any group to split : got to the end of the function and check the communicator consistency (it allows to check it without any problem when 1 proc split groups into sub groups and the other one not.

Patch error in check_intNodeComm : the coordinates were compared with != operator instead of a comparison with a given epsilon.

Remove an MPI deadlock added be the call of the PMMG_check_extNodeComm/FaceComm functions in grpsplit: if 1 proc needs only 1 group and the other needs multiple groups, the function is called only by one proccess...

Change the way we scale the mesh in parmmg to be more consistant (needed for the node communicator construction from the faces ones) : now we scale the mesh for the analysis step (parmmg.c) then we unscale it. And we scale it again for the mmg call. It is immediatly unscaled.

Patch missing header inclusion and add reduce to avoid deadlock in the build of the node communicators from the faces ones.

Feature/build node comm

See merge request dobrzyns/ParMmg!2

Add the free of the mesh without triangles if we don't have enough memory to rebuild them

	- PMMG_parmesh_Free_Comm : to free only the communicators
	- PMMG_parmesh_Free_Listgrp : to free only listgrp

	- if the mesh is valid, parmmg should continue
	- if the mesh is invalid, it is a strong failure

Bug fix in libparmmg1.c : the tetra flags was not reset and so something the computation of the vertex ball was false

change the face storage in the face communicators to add the index of the vertex from which we want to start travelling the face vertices (now we store 12*k+3*ifac+iploc.

Patch a bug in the hashGroup function : the hashTable was reallocated but hash->max was not increased.

Bug fix in PMMG_create_localMesh : the link of the mesh was missing (npnil and nenil can be equal to 0 even if np!=npmax etc..