Initial String Catalog Migration

[Clstroud]

closes #741

• Migrate the previous .strings files to Xcode String Catalogs
• Prune stale translations that are no longer used
• Remove a couple of translations that should not be translated (a debug setting and an unused Voice settings key)

More work is needed to determine how we want to manage these strings overall. If we shift to a pattern defining them 100% in code, we can leverage the defaultValue argument of String(localized: ...) and have untranslated strings fall back to the development locale instead of a raw key.

[Clstroud]

Merging this so we can see how Crowdin reacts to the changes (if at all)