Extend Force sub-counters

Extend Force sub-counters

Need more data for understanding performance variation

Implemented subcounter "restart" and used it for accumulating
position-restraints time with FEP to the position-restraints
subcounter.

Noted TODOs for some future extensions not currently possible.

Also added logfile output from GMX_CYCLE_BARRIER where people
analyzing the performance will see it.

Refs #1686

Change-Id: I9d60d0a683f56549879bb739269e9466c96572c4