Locale files need pruning

[farridav]

The locale files we have should not be translating strings that are already translated in other packages, especially not Django ones (as they have fantastic language coverage)

We need to go through all of the translation files, and ensure that it is only unique jazzmin strings in there.

If a string is pulled in from another package, then it's likely we changed that string and it no longer matches the original translation key, we should revert this to match the original implementation, to improve translations and reduce maintenance.

The CLI script we have that removes known Django and admin doc strings might need updating

Furthermore we should probably add all Django supported languages to the language chooser in the demo app, that way we can see what's missing from each language.