Improve 'organizing' apps and services

Created by: fonfon

With the increased amount of services and applications that are fortunately available for FreedomBox, our current approach of handling apps -- to just display a list of all available apps -- will become less and less convenient.

The dashboard (see outdated proposal #20 ) should help to only display the installed apps, but we (hopefully) will also need something to easier group and search the available apps/services. I'm thinking about something like a "Software Center" or "App Store" (although I wouldn't call it 'Store'). Or just a possibility to group the existing apps into different categories.

We could add this search functionality to the main Apps landing page (/plinth/apps/).

Right now this is not really necessary, but we should keep it in mind or prepare first steps towards this direction.