Issue 1964: Enhance filter possibilities for reviewboard emails.
Issue 1964: Enhance filter possibilities for reviewboard emails.

Adding 'X-ReviewGroup' header to the review mails

Verified using python smtpd.DebuggingServer module.

Fixes bug 1964
Reviewed at http://reviews.reviewboard.org/r/2204/

chipx86/reviewboard,1tush/reviewboard,chazy/reviewboard,KnowNo/reviewboard,atagar/ReviewBoard,1tush/reviewboard,brennie/reviewboard,chazy/reviewboard,sgallagher/reviewboard,chipx86/reviewboard,davidt/reviewboard,KnowNo/reviewboard,Khan/reviewboard,Khan/reviewboard,beol/reviewboard,atagar/ReviewBoard,atagar/ReviewBoard,bkochendorfer/reviewboard,1tush/reviewboard,brennie/reviewboard,davidt/reviewboard,chipx86/reviewboard,reviewboard/reviewboard,brennie/reviewboard,KnowNo/reviewboard,Khan/reviewboard,Khan/reviewboard,chazy/reviewboard,reviewboard/reviewboard,1tush/reviewboard,bkochendorfer/reviewboard,chazy/reviewboard,atagar/ReviewBoard,beol/reviewboard,1tush/reviewboard,custode/reviewboard,sgallagher/reviewboard,KnowNo/reviewboard,chazy/reviewboard,atagar/ReviewBoard,1tush/reviewboard,atagar/ReviewBoard,1tush/reviewboard,bkochendorfer/reviewboard,chipx86/reviewboard,chazy/reviewboard,custode/reviewboard,beol/reviewboard,sgallagher/reviewboard,Khan/reviewboard,chazy/reviewboard,Khan/reviewboard,custode/reviewboard,davidt/reviewboard,atagar/ReviewBoard,Khan/reviewboard,davidt/reviewboard,chazy/reviewboard,atagar/ReviewBoard,atagar/ReviewBoard,beol/reviewboard,Khan/reviewboard,reviewboard/reviewboard,custode/reviewboard,chazy/reviewboard,brennie/reviewboard,Khan/reviewboard,1tush/reviewboard,1tush/reviewboard,sgallagher/reviewboard,bkochendorfer/reviewboard,reviewboard/reviewboard