Introduce MPI in NonLinearMechSolver

- fixed MED node ordering
- polished 64 bit Cocoa Mac OS X FLTK version
- updated copyright

- invert #define logic (HAVE_MESH, HAVE_POST, HAVE_SOLVER, ... instead of HAVE_NO_MESH,
  HAVE_NO_POST, HAVE_NO_SOLVER)

better gestion of remote messages ("a la getdp")

finished up first pass at remote view management:

* interactive stuff is now almost feature-complete (including
  multi-step, axes and adaptive refinement)

* plugins can now be executed on remote views

* renamed GmshRemote->ConnectionManager & GmshDaemon->GmshRemote

refactored the solver code (new GmshRemote class to handle all remote
executions, including solvers)