More XAct Fixes

A few more fixes to our XAct playback:

 - We now obey loop counts on played cues.
 - We now support "New Wave on Loop" feature.
 - Decoded the "Play Release" flag in sound bank format.
 - Non-complex clips now have correct volume.
 - We now decode the per-clip volume.
 - Moved all XactClip decoding into one place.

Tested this against XNA in a test game project and it all seems to behave correctly.