Gen 3's getDamage is a clone of an older Gen 5's version.
Delete it for now, since it has no reason to exist until differences
in that function have to be added for gen 3.
During initialisation of Tools, each new mod no longer makes a copy
of every data object from the parent mod. Instead, a new object is
created when and only when the mod actually makes changes to a
particular object. In other words, this is a "copy-on-write" system.
Damage categories are now read using .getCategory, which gen 3 overrides.
move.category can still be read directly to check if something's a status
move, but it should never be used for reading damage categories.
This also fixes a crash in gen 3 and makes it playable again.
