Consider moving board definitions to firmware repo

[neilenns]

The board definitions are intertwined with many of the firmware #defines so it might make sense to move them to the firmware source repo.

Questions to answer:

1. Can the board definitions get automatically packaged up with the firmware binaries on releases and pull requests?
2. Can the board definitions get downloaded by the same firmware download script and put in the right place for connector builds?
3. Should downloading board definitions and firmware be a pre-build step for all connector builds?
4. If board definitions are removed from this repo what's the developer experience the first time you build and deploy? Will no boards get detected? (see 3. above as a possible solution)