Add source for bavaria.

[arnesetzer]

Hope I did everything correct 😅

Source for https://github.com/whosonfirst-data/whosonfirst-data/issues/2032

[stepps00]

Aside from some minor changes to the usage and prefix values, this looks great.. let's hold off on merging until a PR with data updates is ready to merge.

[nvkelso]

@arnesetzer Please rerun the makefile to resolve the conflicts.

[arnesetzer]

Done