better format for the output of Roland_Sylvain gravity integrals, added output of the norm of the g vector, and added an exit message if the solver is run with ROLAND_SYLVAIN = .true. (only the mesher is needed in that case, since we compute some integrals on the mesh and then we are done, no need for a time-domain solver)
Merge pull request #75 from komatits/devel

better format for the output of Roland_Sylvain gravity integrals, added ...