Load button groups from bitmap

[qqii]

Todo:

Translate code into bitmap @grant-m-s

Complete button group implementation for combo requirement and delta height to drop (or height to drop to)
That will use up the remaining channels

[grant-m-s]

works but you should remove all the print statements

[jnterry]

Me, Raef and Grant have just had a discussion. Tilo's feedback emphisises the importance of group mechanics, and to achieve that we may want to support more interesting button mechanics.

Eg a 5x5 dance pad area where 1 or more players must move around following a pattern (with tiles lighting up in advance to show where to go next). Groups of buttons that must be stepped on in sequence, by multiple players, etc.

Mechanics this complex cannot be encoded in a bitmap
but requires programmatic control over the buttons. The main draw for the bitmap loading is preventing needing to type out the wall groups. I would suggest loading the wall groups from a bitmap, and then say that our programmatically added button will cause wall group n to fall when successfully triggered.

[qqii]

This currently supports "buttons groups" and "wall groups" like what used to exist. Both of these groups are encoded onto a bitmap. I'm just going to say that at least for this pull request allowing for a dance pad is going to be out of scope, I'd make a new issue as an enhancement, as loading "dance mat pattern style button groups" will most definitely have a different loader/system.

So give that will it be okay to merge if I remove the print statements?

#121