Updating FBO usage, adding config GUI

 - FBO usage updated to be more same.
 - GUI rendered once per scene to seperate FBO, then blitted to quad
   positioned in world
 - Main menus now rendered onto main GUI FBO, and run through VR
   Renderer (riftifying the whole process)
 - Added Minecrift GUI for setting Oculus/VR headset specific options
 - Making getchanges.py script clean up before diffing, preventing
   unwanted files from continuing to exist.
Updating JRift submodule