Status taxonomy: Add checks to add meaningful status to listings

We have status taxonomy, that is supposed to signal the maturity of the app.

To do's for this are:

• add a status to all listed apps
• add pre-release status to all apps that have not tagged a release
• update status regularily

To make this doable, we need to come up with

• clear criteria for which status fits
• a checker, that can automatically suggest a status for an app based on these criteria.