Fix for Ungrouped Bug

Current behaviour:
* Ungrouped group management gives errors in languages that have it translated.

Summary of changes:
* Prevent "Ungrouped" being translated in the URL and as the group_id
* Add a test to check that "Ungrouped" will always display without error in Spanish, which has shown the bug most frequently.
I think there was a way to fake out the installation of a language pack without needing to download it from the internet? Or does it know to do so so within the context of tests anyway? @aronasorman?