Fred: comment out currently unused zone cfgs
Fred zone priorities: rename moves_away -> hp_enemies

because that’s really what it is.
Fred zone priorities: add number of enemy calculation

It isn’t directly needed here, but trivial to add.  As a result, code
duplication in the zone holding evaluation can be avoided.
Fred zone holding: do not count enemies that can get to zone again

This is already done in the zone priority evaluation (and as of the
previous commit, it is saved in the zone cfg).
Fred zone holding: remove x/y parameters from cfg.hold

They are not needed any more.