Changes

Mergeduty is responsible for performing branching + code uplifts, and making sure the automation is ready for those branches and merges. The steps that need to be performed alternate; we're basing this on whether mozilla-central will become an odd or even numbered Gecko version after Merge Day. (See: [http://whattrainisitnow.com/ What train is it now?] and [[RapidRelease/Calendar]])