Rendering engine overhaul

This change has been in the works for a while. The main benefit is twofold:

1. Improved performance. About 30% more fps
2. Elimination of jagged edge artifacts on particles.

The graphics engine uses deferred rendering. There are 2 frame buffers that are required: Color and Depth. Previous Depth buffer was built in a separate rendering pass, which basically required the whole geometry to be re-rendered twice, once for Depth and once for Color pass. Now both of these buffers are built in a single pass which significantly increases performance. The artifact elimination comes from improved depth buffer precision.

A lot of players on integrated graphics cards have been reporting poor frame-rates, this update should help keep FPS more reasonable on lower end graphics cards as those.

These changes will be shipped with the next patch. We're still working on other parts of it, it should be ready in about a week.