AMYboard release tags

We want to eventually ship multiple firmwares for AMYboard, a `dev` version for recent development that may have more bugs, and a `release` version that has had more testing. That's not too hard on its own - we could have `./release.sh` take a `release_tag` parameter and make sure the firmware updaters know which one to use. But the webapp and the firmware are linked in code, a `dev` firmware may require a `dev` webapp as well. We could have a separate `dev` website like `amyboard.com/editor-dev` , or we could also have the webapp detect the tag of the current firmware on first "pull" (syncing) and set the parameter and code path there. A nice upside of detecting on sync is that we could also alert the user if their firmware is out of date (no matter what tag they were on)