Redirecting map.bafu.admin.ch auf topic=bafu

The aim of this PR is to suppress https://github.com/geoadmin/mf-redirects

* If map.geo.admin.ch is called, then the `topic` `bafu`is selected.
* Needs a new ServerAlias 'map.bafu.admin.ch

To do:

1. Merge and deploy
2. Add `map.bafu.admin.ch` and make the DNS switch