Change MPI setup to communicate TPR as buffer

Change MPI setup to communicate TPR as buffer

Changed the initial setup of nodes to communicate the full tpr file
buffer instead of using the individual calls for the fields.

Now non-master nodes receive the inputrec and mtop
and populate them themselves.

Refs #2971

Change-Id: Id4f3739a978ca507dacc45c78a8a75368cfe86fd