Add a filter on project browsing pages for release status

Users should be able to filter the project browsing listings based on the release status of a project. Whether a project has stable releases (and whether it is opted into security advisory coverage) are all factors that a user discovering modules might want to use when factoring in which modules to use.

Production outage: No
Change affects: Drupal.org project discovery
Deployment schedule: week of 2017-04-03
Backout plan: revert or fix in place