Add text based patterns

Signed-off-by: Paul Brook <paul@nowt.org>
Rework 8x8 cube mapping

Signed-off-by: Paul Brook <paul@nowt.org>
Swap buffers after clear on shutdown

Signed-off-by: Paul Brook <paul@nowt.org>
Set brightness

Signed-off-by: Paul Brook <paul@nowt.org>