Animation system improvements

[Admer456]

In Q3, animation is plain simple. It's controlled by a simple frame variable.
However, it'd also be nicer if we could have an "animationID" variable, as well as a way of programmatically controlling bones (bone controllers) from the game DLL.

Eventually, animation channels could become a reality. Two animation channels should be perfectly enough, although up to 4 could be provided.

This would require several modifications to the renderer, networking and how animation defs are read.