Catch exception thrown by capnp to get improved error message.
Catch exception thrown by capnp to get improved error message.

This fixes an issue I had where a capnp exception went uncaught and
the libmesh terminate handler was called, but no nice error message
with line numbers, etc. was printed.

libMesh/libmesh,BalticPinguin/libmesh,dschwen/libmesh,libMesh/libmesh,BalticPinguin/libmesh,BalticPinguin/libmesh,BalticPinguin/libmesh,dschwen/libmesh,jwpeterson/libmesh,dschwen/libmesh,BalticPinguin/libmesh,jwpeterson/libmesh,BalticPinguin/libmesh,libMesh/libmesh,libMesh/libmesh,jwpeterson/libmesh,jwpeterson/libmesh,dschwen/libmesh,jwpeterson/libmesh,dschwen/libmesh,dschwen/libmesh,libMesh/libmesh,jwpeterson/libmesh,dschwen/libmesh,libMesh/libmesh,dschwen/libmesh,jwpeterson/libmesh,libMesh/libmesh,BalticPinguin/libmesh,BalticPinguin/libmesh,libMesh/libmesh,jwpeterson/libmesh