Especially for the installed module (which is probably the case if you
use production.ini), this makes more sense than referring to the source
location.

We leave the development.ini for now, as there it might make sense to
read the local directory (although it's probably installed as an
editable module anyway).

Those things are not really a configuration thing that changes, rather
they are part of how the code of the application works. As such, it
doesn't make too much sense to require those configuration values.
Instead, we now add those filters programatically.

This also ensures that the filters are the same between development,
production and testing environment.