Pixel perfect drawing on fullscreen mode

[kerunaru]

As discussed on #27, it would be great to have the sharpest image on fullscreen (not only on retina displays Macs, but on all machines).

An inspiration to accomplish this can be how openEmu project make the emulators' view drawing where you can also select what filter to apply to the image while running (I have no idea how they implement that but I though it could be a great place to research).

Brainstorming time!