Animation support

Spent the weekend extending my model format to support animation frames, which led to optimizations in the converter to reduce the number of indices generated, which led to writing a new model exporter that can export animation frames, which led to learning how to rig and animate in Blender, which led to writing an animation playback control system, which, finally, led to (simple) animated trees in Silhouette.  So, next update will have trees that sway a bit every so often.  Sweet.  Doesn't sound like a lot of payoff for a bunch of hours of work, I guess, but I'm happy it's there.  =P

The main thing here is that now I've got all the necessary tools to handle real animation, so can make use of that in future projects.  Swaying trees was a good, simple, starting task.  I think the plan for this week is going to be another live wallpaper and I'll be exercising the new tools with it.

Currently the animation is very simple vert-cloud style, which works nicely with OpenGL ES's vertex-buffer centric approach.  Next upgrade will be for proper interpolation between frames -- currently there isn't any so it works best for subtle motions.  I'll see how much the next project calls out for interpolation to determine whether I tackle that sooner instead of later... for now all the data's in place and that's the worrying part.