Make it easy to choose OpenStack versions.

Now it is possible to select components versions for the install
using yaml configurations files and specifying them in the
command line:
* Added new option (--origin) to specify components sources
  configuration file to be used.
* Implemented configuration load (repo, branch, tag) during
  component sources download.
* Remove url parsing logic from downloader and make it work
  with passed configuration.
* Removed components 'get_from' options from configurations.
* Added new sources configuration files for master, havana and
  havana-1.

Implements: blueprint flexible-versions
Change-Id: I35665a309bf8203f10588c01a336e2e62d8e4b5e