Localization Infrastructure for UI

[cynicaloptimist]

There would be a lot of work involved in this, but the actual job is straightforward. Move all of the user-facing strings to a common location in something like an en_us.json and import them for use in their respective locations. This requires infrastructure to also handle strings in HTML files.

Individual localization files would then be easy to add, I've been approached by people interested in Russian and French translations.