Example run.sh script upgrades

I liked your GRINS_RUN idea, and I had to futz with the run.sh scripts again anyways, so:


Allow GRINS_RUN to override LIBMESH_RUN if the former is set

Respect LIBMESH_OPTIONS if GRINS_SOLVER_OPTIONS isn't set

The syntax works with dash for me, so let's only require sh instead of
bash