Add publishing in our F-Droid repositories to the Android jobs

This MR adds the config files needed for publishing APKs in our F-Droid repositories from !124 (closed) (updated for the production system) and it adds a CI job for publishing the APKs built by the other Craft Android jobs.

As in !139 (merged) Digikam and Marble were not added to the project settings because they never had a successful build on Binary Factory.

publishonfdroid.py is run unconditionally for every branch, but it checks if the current project branch is cleared for the service. If it is cleared then the APKs are published with the help of the fdroidpublisher service. Otherwise, the script does nothing. In particular, it doesn't fail because this would result in failed jobs for work branches.