Postprocessing base

[barlebino]

Now we render to a framebuffer, then render a flat rectangle that occupies the full screen. The look of the flat rectangle are based on the contents of the framebuffer. Right now, the flat rectangle only takes the appearance of what would have been rendered if we did not render to the framebuffer

[barlebino]

WAIT! will need to check if it works on my machine

[barlebino]

Should be good now