GitLab

Finally, some automated CI \o/

This is just the beginning. There's a lot more we could do, but this is a good start I think.

It is using the docker image used to test the F-Droid client for now. We can easily provide our own later. Also, we probably want to add lint checking and espresso tests eventually. Soon, we will even be able to deploy master automatically to a nightly builds f-droid repo.

Thanks @akwizgran for providing a server for this!

This might close #468 (closed), or not?