Revert translation to packaged ones per POFile

    * Overview: Provide a way for Translation admins and translation team administrators to revert all translations to packaged (usually upstream) translations for entire POFile with a single action. We need this to help fix the problem of previous open translation teams (we get repeated requests for automatic reversion).
    * Goal/Deliverables: Add UI option for each POFile to revert all translations to packaged ones (where published=True, set active=True; where published=False and active=True, set active=False)
    * Full spec: none
    * Depends on: n/a

We will know we have finished when we can solve request like https://answers.launchpad.net/rosetta/+question/7798 with a single action by going to the relevant translation overview page (https://launchpad.net/ubuntu/feisty/+source/control-center/+pots/control-center-2.0/da), and selecting action 'Revert to packaged' to revert all translations in a POFile.