Also updates the release.sh script to support tagging release candidates and development milestones. Adds zuul configuration to trigger a Readthedocs webhook for the release notes. Change-Id: Ia784b34fb0b740998de72599d4921f9303e41cac
Also adds documentation on releasing to the developer guide. Change-Id: Ic26daf362ce79fa1ea9ce217cf470d85c961affa