Support more than 512 channels

Needs:
- Blocking protocols (bitbang, hspi without interrupt handling) would need to disable the watchdog.
- Proper protection for too fast framerate (make sure to wait long enough for the pixels to latch data)
- Art-Net support multiple universes. Possibly number up? e.g. with 1024 channels and 0,1,2 as universe, use 0,1,3 for second part. When to push out data? on last?
