ADDED basic implementation for the stopmusic command
MODIFIED stopdance to indicate the use of a deprecated method
MOVED stopPerformance code from CreatureObject to EntertainmentService
MOVED stopAudience code from CreatureObject to EntertainmentService
MODIFIED stopdance to utilize refactored stopPerformance code
MODIFIED stopmusic to utilize refactored stopPerformance code
MODIFIED CreatureObject.setPosture to use refactored stopPerformance method