Add support for Ergodox, mcdox keyboards. PJRC build working again.

It's a bit if a beast sorry. This is my first pull request so please be gentle :)

Fixed the broken PJRC build
Added support for the Ergodox (ergodox.org). This was actually cub-ubanic but I've made some improvements.
Added support for the very related mcdox (https://github.com/DavidMcEwan/mcdox)

I'm not sure how to split this down into smaller pull requests but if you have an idea I'm happy to do so.