Fix performance bug in the SmallMover (#4141)
A large fraction of the SmallMover's running time was spent on
creating a movemap so that it could look at one thing inside
that move map, and then destroying the newly created movemap.
Same thing in the ShearMover.
Now, create the movemap once at the beginning of `setup_list`
and use that movemap throughout its execution.
Also, there's no need to call pose.energies().clear(); an @details
has been adde to the Energies class to explain why the `clear`
method would ever be necessary.
Running time in a small-mover-only protocol drops 90%!