Added some tag related functions to git module
Simplified git-bloom-import-upstream

Now it only takes an archive and imports it into
the upstream branch and creates tags. The export
of the upstream repository is now handled by
bloom-export-upstream, which creates the archive.
The logic to automatically determine the version
is now handled by git-bloom-release.
Convert to yaml from json and improve config edit
Finished refactor of git-bloom-release