FMod MusicSystem integration

As a part of a course in my master studies we had to implement FMod Wrapper classes for MOAI. Me and my colleague implemented the MusicSystem and some more classes like MusicInfo and MusicEntity that are needed within MusicSystem.
The code itself was compiled and tested as far as we could but is not guarenteed to work since the class MOAIFmodEventSystem is still missing and needed for our class to work.

The includes and classed are included/registered in moaicore if USE_FMODMUSICSYSTEM is defined

It is required by our advisor to do a pull reqest