Partial progress on reenabling REMD.

git-svn-id: https://svn.ices.utexas.edu/repos/clsb/trunk/moil@4865 90e2fc84-bd37-0410-82f1-ae2f889bfac2
Disabled REMD if MPI is also disabled.

git-svn-id: https://svn.ices.utexas.edu/repos/clsb/trunk/moil@4866 90e2fc84-bd37-0410-82f1-ae2f889bfac2