not include feel/feel.hpp
use worldcomm from mesh
use worldcomm from mesh worldcomm
use sequential worldcomm define in Environment
use worldcomm from backend
add worldcomm arg in the backend()
use worldcomm form test space
remove useless header
not use feel/feel.hpp header
up mesh build from vtk triangulation
update oplagP1 :
 - start use of non blocking communication
 - use worldcomm from functionspace given
 - clean file