fbdev backend

Add support to use fbdev as a backend to paint directly on Linux console. It will not be the fastest one (it will be software rasterized), but it's easy to implement and could be a starting point to move to better ones. The most simple implementation would be to just paint the canvas pixels to the framebuffer device each time a `frame` event is dispatched. This could allow to have [basic graphics support on NodeOS](https://github.com/NodeOS/NodeOS/issues/39#issuecomment-77125958).