Translation request deduplication

[ArtOfCode-]

Translators would like to be able to:

• Mark an issue as an exact duplicate.
  • Changes to the master should copy over to the duplicate [?].
  • Edit links to the duplicate should redirect to the master's edit page.
  • If the duplicate is associated with a broadcast item, that broadcast item should have its translation request reassigned to the master.
• Make a note that a translation request has issues.
  • The Translation model can have a new field to store these.
  • There should be a new status, Translations::Status['On Hold'] to indicate that a translator has indicated problems. This status should not remove the TR from the open TR list.
  • The page to add these notes needs to include a note that the issues will not be automatically notified to the author; the translator needs to forward them manually.

[ArtOfCode-]

Done with 29a6440 and 91e51bb