Make Hide/Show objects more dynamic

be on the look out for more static ids in the wild
unused constants are still included because a
script could be written to check whether the player
has picked up an item/fought a legendary etc.
Enumerate hide/show constants
Merge branch 'master' of https://github.com/dannye/pokered

Conflicts:
	scripts/ceruleancity.asm
	scripts/mtmoon3.asm
	scripts/pewtergym.asm