Bypass language selection dialog for Schema Config when there's only one language

[bronwyncombs]

See Nate Shoobs' request via Discourse:

Documenting a minor annoyance here, but one I know a few other collections share.

If a collection database only has one localization (English), the user should not be prompted to select a language every time they open the schema config. It should just take you directly to the list of tables.
That extra click and extra load time it takes for the DB to display the list of localizations really adds up when doing a lot of work on the schema.

Additional Consideration:
The language selection dialog is also where the option to add a new language is found. Fulfilling this request would also require moving that option somewhere else. I'd think that near the "Change Base Table" button on the main page or under "General" in Preferences would work fine.