Attempt translation of menu apps and models in case user has marked them as translatable in settings

We have custom django-suit menus in our project's settings and have just made everything translatable. The `_ = lambda s: s` trick in settings allows us to mark which strings should be translatable in the settings file and the `makemessages` command picked them up but django-suit wasn't using them. This branch fixes that and hopefully these are the correct places to be doing the `gettext()` lookup.