Extends the ExternalChangesetState by DRAFT (plus UI representation)
Adds drafts to the calculation of historic changeset data
Exposes the number of drafts on the changesets.stats and on the changesetCountsOverTime fields
Still to be figured out:
Do webhooks need a special treatment or will they just work? (Maybe there will be pointers in the reviews.. ) Otherwise I'll give it a shot tomorrow.
Can be reviewed commit-by-commit.
