Added try/catch statements in OpenMP regions and tMPI start

Added try/catch statements in OpenMP regions and tMPI start

OpenMP cannot handle exceptions when they are thrown inside an
OpenMP region, but caught outside of it. Instead we catch these
exceptions inside the region and exit with a fatal error. Not
beautiful, but at least we will know what happened, and exceptions
should only occur in catastrophic scenarios in parallel regions
(where we already call the fata error handler). For trivial OpenMP
blocks that should never through there are comments noting this, so
we remember to add a try/catch pair if necessary in the future.
There is also a new catch-all in the tMPI entry point function.

Refs #1828.

Change-Id: I52103a076b7f0a5e8ac1f740160e4de0fa97f638