EMI: Costume fixes and cleanup

Instead of resetting the costumes when a wear chore is started, costumes are freed as soon as they are no longer playing any chores. This makes it possible for an actor to play multiple wear chores simultaneously, which is what the milk bottle in the set lav does (see #878). This PR also corrects the behavior of some opcodes in the case when an actor has multiple active costumes.

I also removed the special treatment for wear chores in Actor. I'm fairly certain this is not necessary anymore, and so far I haven't spotted any issues.