i.e. it now supports stuff like MULTFLT in the schedule
section. Possibly, the MPI-parallel code paths need some fixes. (but
if the geology is not changed during the simulation, the parallel code
will do the same as before.)
the most fundamental change of this patch is that the
reference/pointer to the DerivedGeology object is made
non-constant. IMO that's okay, though, becase the geology can no
longer assumed to be constant over the whole simulation run.
