Better audio design

[rhelmot]

Right now we are kind of just swaying in the wind in terms of what music/ambience events are playing during gameplay - we set some stuff at the start, but we allow any gameplay element to change them as they please, and boy do they change them. The music track changing whenever you find a cutscene is arguably a feature, but the ambience changing is an issue - you can only hear wind effects when the ambience is set to ch4 or a specific ch9.

So, wishlist:

• have some mechanism which overrides any change to the ambience to make sure we can hear the wind
• have some mechanism to track progress through the map and apply that to the current music track, via either progress parameters or layers
• in order to support all this, config for each music track indicating how to manipulate it based on progress, side paths, etc
• config to be able to tell when a room will change the music and react accordingly