Support FBO Rendering

Idea is to step away from rendering directly to our opengl context's default framebuffer, but to render to a FBO and then to the default framebuffer.

While this opens up the following possibilities:

• increased depth buffer
• post-processing
• ability to render to target resolution and later upscale/supersample

It is still unknown if this will have an impact on performance but in terms of FPS and also latency.