Add utility function to add pending op to tweet.
Replace UPDCF flags with a more flexible pendings flags mechanism.
This is primarily to avoid having all pending ops also depend on the
user profile image. This is most relevant for bulk filters.
This also attempts to make pendings flags less incomprehensible.
Fix IsSingleAccountTPanel false positive for highlighted/unread panels.
Fix DB load of multiple retweets of same tweet duplicating source parsing.
This also fixes changes to a tweet (eg. flags) which result from
applying a filter to a tweet just loaded from the DB, being immediately
overriden by a duplicate parse of the same tweet caused by also loading
a retweet of the same tweet in the same DB load operation.