Project translations overview page: explain what the viewer can do

Still show link to translation group because that's where you can start a translation team for your language. Document this on the page.

Options for what you can do are:

 * review and translate directly (maybe just translate directly if it's an open project)
 * translate (suggest).

Since a person can translate into multiple languages it is not easy to use this wording:

"You can review/translate translations in language X for Project Y"

We can replace X with a list of languages... but in some cases the list of languages can be quite large.

------------

We should have a different text for each translation policy, in accordance to that person membership in the l10n teams.

Here are some ideas:

Open:
  You can add and review others translations for all languages

Structured:
  You can add and review others translations for LIST OF LANGUAGES
  You can add translation suggestions for all other languages.

  You can add translation suggestions for all languages.

Restricted:
  You can add and review others translations for LIST OF LANGUAGES
  You can add translation suggestions for LIST OF LANGUAGES (!!! IT CAN BE QUITE BIG !!!).
  You can not add translations for all other languages.

  You can add translation suggestions for LIST OF LANGUAGES (!!! IT CAN BE QUITE BIG !!!).
  You can not add translations for all languages.

Closed:
  You can not suggest translations, since you are not a member of any translation team appointed by TRANSLATION GROUP
  You can add and review others translations for LIST OF LANGUAGES

This would be good to do but is not on our current roadmap. Patches solicited!