Fix too much recursion error during update_location_tree. Don't traverse...

... descendents during the all-locations update. Actually disable update_location_tree during prepopulate. Add tests for update_location_tree.
That was not exactly what I meant ;)
I was actually proposing a method to temporarily add a stream handler for a string buffer, and to remove it again - merely returning the buffer for inspection.

This getter seems superfluous, tbh.