Fixed performance issues

Used a combination of previous non-visible cube culling, instanced
rendering, bounding frustum culling, and a more efficient physics engine
construct.
Regression bug exists where character will spawn in middle of world if he
falls off the edge.
Updated shader

This commit does not affect the compo version of the game; this commit
only exists to allow the compo version and post-compo version to use the
same asset. The only thing changed was the instancing vertex shader, which
goes unused in the compo version.
Merge branch 'master' into post-compo