Added player music functionality

Refactored how the HashMap "performances" works in EntertainmentService.java to have a key consisting of the name and the audio id of the performance. I did this because those two values together uniquely identify each individual performance.

I also added the command "startmusic". The command command should the correct music (I tested with a few songs, and they all seemed to match up properly), it should correctly animate the player for most instruments (when I tested mandoviol the character didn't animate during the song intro), and it should properly send most music-related messages to the player.

Known bugs:
-It seems that the intro animation for mandoviol doesn't work.
-Calling the "startmusic" command with no arguments properly presents an SUI window with a choice of songs that the player can play with the current instrument, however it doesn't appear that the list is complete. Also, I'm not sure how the list should be sorted, so currently it is not sorted at all.
-The "stopmusic" command is not implemented yet.
-Switching instruments while playing simply switches the instrument, this is incorrect behavior.
-Calling the "startmusic" command while already playing causes the new song to be played (I know how to fix this, I just haven't yet)