* Factor out the code for moving tags from tag aliases to a separate
TagMover class.
* When aliasing two tags that have conflicting wikis, merge the old wiki
into the new one instead of failing with an error. Merge the other names
fields, replace the old wiki body with a message linking to the new
wiki, and mark the old wiki as deleted.
* When aliasing two tags that have conflicting artist entries, merge the
old artist into the new one instead of silently ignore the conflict.
Merge the group name, other names, and urls fields, and mark the old
artist as deleted.
* When two tags have conflicting wikis or artist entries, but the old
wiki or artist entry is deleted, then just ignore the old wiki or
artist and don't try to merge it.
* Fix it so that when saved searches are rewritten, we rewrite negated
searches too.
f0299a8945