Add OpenStack upgrader to fuel-upgrade

OpenStack upgrader performs the following tasks:

* add information about new releases to Nailgun
* add notification about new releases to Nailgun

blueprint upgrade-to-5-0-1

Orig_Change-Id: I962921492e09e06eb0396fae26c4bea1774720df

Notification topic is changed to "done" - it's the difference from original commit

Change-Id: Id15e686136b0df722274329c81033aef276ca7d5