release start: Refactor branch deployment to QA

Created a top-level deploy command that is either available on its own
(as flow deploy release x.y.z qa) or is automatically incorporated as
the last step in release start.

Signed-off-by: Ondrej Kupka <ondra.cap@gmail.com>
Finished feature 54107089/deploy-on-release-start.

Signed-off-by: Ondrej Kupka <ondra.cap@gmail.com>

Conflicts:
	gitflow/bin/__init__.py