Some database parameters are required if the type is `mysql` or `pgsql`.
Also, the variants of the parameter --database-type decreased to those
that work with the configuration, as it is directly mapped to the
parameter.
The functions in `map-conf-changes.sh` where extended to support the
conditional mandatory argument to throw an error if this parameter is
set.
This type should work, but there are still many things to do here to
work nice and well.
Things that currently not work (well):
- not all parameters work for now
- nextcloud installations in subfolders (e.g. slashes in the object id)
