Rename 'Sleep Clause' to 'Sleep Clause Mod'

This new naming style is to acknowledge that Sleep Clause Mod represents
a mechanical change to the base game, because it causes Sleep status not
to be applied in cases where it would be applied in the base game.
Fix some misleading comments in formats.js
Report HP as percentages (except VGC and Custom Game)

In VGC, HP continues to be reported as pixels. In Custom Game (and other
debug formats), health is reported as exact HP.