First major pass at Rendering in Large Scale Domains

Lots of changes here, but the basic idea is this:
- New HiFiVec3 class that handles 64 bit encoding of large scale/definable precision positions
- New classes for wrapping up rendering at large scales: GlobalRender, LocalRender, VoxelSpaceRender
- Change to how we set up the OpenGL model view so that it's origin is actually at the camera location so things are rendered relative to the camera. The result is that we get more accurate rendering even when camera location is at large distances.
- Changes to Application, Avatars, VoxelSystem, etc to use new rendering origin