Bug 1032978 - Added event_group, chunkNum and chunkTotal to build properties in process/release.py, r=bhearsum

--HG--
extra : amend_source : ff59acb8fbe306aa042efd7551c117215c6e9479
Bug 1049099 Thunderbird Linux and Mac MozMill builders are using the system python. r=nthomas
Merge branch 'master' of https://github.com/mozilla/build-buildbotcustom into signtool-with-formats