In this custom mode, odd lines use MODE 0 (wide pixels, 16 colors), and
even lines use MODE 1 (square pixels, 4 colors).

- Add a settings window to the 8-bit effect where you can chose what you
want to draw
- Add the customizations required to make it work in graph.c
- Tweak some other places so it is easier to add other modes later on.
- Groundwork for some more modes: EGX2, ZX spectrum, Game Boy color.