Allow for a quick and easy way to back out from an RMSE upgrade

The auto update works really well, and the ability to approve an upgrade is the cat's meow. Thanks!
But no matter how well an upgrade it tested, there is always the potential that some unintended bug will be introduced that can knock a station right off the air. Making that station stay off the air until a fix is found, coded, tested, and pushed out does not seem right. Plus, there is the potential that the station might be needed right away.
Some ground rules to address WDT concerns: the back out would only be available to stations that are on the very latest release, and can only be backed out to the immediately previous release. As before, no support for stations running anything but the latest release.