Ensure domains are large enough for atom motion

Ensure domains are large enough for atom motion

The introduction of the dual pair list has led to larger nstlist
values, which leads to larger atom displacements between domain
decomposition steps. This has made it much more likely that
"atom moved to far" errors appeared at DD and PME redistribution.
Now minimum DD cell size setting correctly takes into account atom
displacement (when there is a reference temperature).

Note that this can significantly increase the minimum DD cell size
for solvent systems and slighlty for systems with large molecules.

Fixes #2614

Change-Id: Ie41131e9eed3ef828928516a6b8ebfb9b5ba2bdb