Added option of using previous steps strain rate to soften materials, updated only at the end of the previous step

Reverted to using 'include mpif.h' as the use of mpi.mod requires the MPI module be compiled with the same compiler as the DOUAR source, which is not true on geodyncomp

Added params to the list of things passed to the vrm.f90 subroutine (for use of an initial strain rate with plastic materials). Modified to use either an input penalty value or bulk viscosity