Remove mdrun -seppot

This output of rank-local energies is not needed for any routine use,
and isn't much use in mdrun -debug either. Removing it simplifies a
few code paths, including removing some dependencies on writing sane
things to the log file. Eliminated some now-unused parameters.

Refs #1292

Change-Id: I7628b78862144ae2478b6f42a6818915e3a22fe3