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

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extra : amend_source : ff59acb8fbe306aa042efd7551c117215c6e9479
reverts reboot logic in scriptfactory
Bug 1049099 Thunderbird Linux and Mac MozMill builders are using the system python. r=nthomas
Merge branch 'master' into clone_less
adds tools_repo_cache to ScriptFactory
adds tools_repo_cache to ScriptFactory and MBF. also adds condition for cloning mozharness in misc.py
Merge branch 'clone_less' into clone_less-dev