Move ownership of kinetic energy object to ISimulator

Move ownership of kinetic energy object to ISimulator

Treating the kinetic energy object (ekind) equivalently to the
energy object (enerd) makes subsequent changes easier. It also
removes some code duplication between do_md, do_rerun and
do_mimic. There are some algorithms that never use the kinetic
energy (e.g. minimization), but this is true for other members
of ISimulator as well.

Change-Id: I995d14652dae25bcbcaa0a75437382a053e76f74