Implement content-translation workflow

[Anthony Lenton]

Summarizing an email conversation:

 * 'Translations' should be something that you do after an initial submit. You submit translations separately, to avoid creating an initial submition process that takes too long.
 * Put 'Translate my app' in the main navigation and add a link to it on the 2.1 My Application page, so there are two ways we can encourage people to supply translations.
 * Add "Show other languages provided" (for this app) to the 2.1 My Applications

When translating an app, provide a workflow which goes:
- Select language you are translating into, distinguishing languages that already have a translation from untranslated ones.
- Then we show the forms with the translatable fields side-by-side with the fields in English that we added originally.

Re: Translations moderation: We'll leave translation updates unmoderated initially.
Rationale: Lets focus on making an English version public and available swiftly and efficiently and then add this additional layer of complexity. If we try and tie translations into the initial submit process it could quickly get very complicated. By forcing this into a separate flow we can keep clarity and treat each language as a separate review.