Add monochrome_pixel - A jagged/pixelated version of monochrome with no wallpapers.

Created by: lasers

The pixel theme is not completed and some icons requires to be pixelated first... meaning nobody really can use pixel theme right now... At least not without seeing polished icons.

I made a slightly pixelated version of monochrome along with two wallpapers (classic + full) for myself. Maybe we can have rgui options in xmb to generate proper checkered pattern. 😄