Fix number item issue with buyer NPCs

The intermediary numberitem stack wasn't being deleted if the NPC
already had a stack of that item, and for rainbow ferns this was causing
dangling timer issues. These are now deleted properly.
Simulated attacks
Comment, bugfix, off/def parameter addition.

Remove DefendingHit to stop target gear breaking. Allow offense and
defense as parameters.
Change to godlog, improvements
Add SimulateCast

Requires both players to be online, simulates cast with the given
spellpower or what the caster has at the time.