Added VAOs, frame rate counter now returns literal FPS.

- GLTextureEngine.java: Now featuring Vertex Array Objects (VAOs), which
are apparently used to encapsulate Vertex Buffer Objects (VBOs) and
their matching shader Attributes. Hopefully this will work, I am running
out of ideas.
- GameEngine.java: GetFrameRate now returns the actual number of frames
that were drawn in the last second, instead of a messy extrapolated
value.