The official installer now requires the user to log in which we can't
really do in a scripted manner. Let's see how long this way of
installing things will be available.
While doing this remove an ancient hack of some Qt settings that we no
longer need.
This also tries to prune some things that we don't need in the Docker
image to reduce image size.
The mapbox plugin is removed as it would add a dependency to QtSql which
we otherwise don't need. And since the plugin isn't used, no point in
installing it.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
