Previously only one gerrit_id for user_profile was supported and took
part in record_processing. In case of using multiple Gerrits or multiple
gerrit_ids in one Gerrit, while merging profiles all except one
gerrit_ids were rejected.
This commit adds new user gerrit_ids user_profile key containing all
required mapping between multiple Gerrits and gerrit_ids. Each gerrit_id
acts the same way as old gerrit_id during review record processing, that
potentially increases success rate of record identification and
decreses amount of unnecessary launchpad user queries by storing user
with all gerrit_ids as a primary key instead of one.
Also changes to UI added to represent multiple Gerrit accounts.
Change-Id: Id20c7ed46cd409946b9a5247a94331860895f859
8b5345b458