Options tile_weapon_offsets and tile_shield_offsets

These allow setting custom weapon and shield tile x,y offsets for use
with tile_player_tile. If only one offset pair is set, the other will
be taken for the hard-coded entries in mcache if they are available,
so the player doesn't have to figure out e.g. weapon offsets when they
only want to adjust the shield.
Fix missing space in br.end and zig milestones (rchandra).
Don't generate buggy buggy jewellery.
Fix ring ID
Replace LAST_FORM with NUM_TRANSFORMS

There are no longer too many switch statements!
Add hydra form
Cleanup cleaving checks
Add Hydra Form spell
DEVOUR THY FOES

Now respects god conducts. Thanks, magicpoints!