[enhancement] Add "moderated" state

[LPABelgium]

Hi !

Just a suggestion for enhancement.
With a complete moderation system, have a "moderated" state could be a good enhancement to this package.

Something like :

• Moderated : boolean
• Moderated_by : integer (ID)
• Moderated_type : model (admin)

Approved alone is not suffisant because a non-approved comment will appear again and again on the "comment to approved" list.
But if we can add a second filter to get "non-approved" and "non-moderated" comment, we'll have only comments which are still to moderate.
Of course you could say "non-approved" comment has to be deleted. Ok...but not always. Some customers want to keep a trace of all comment deposed on their website, approved or not.