* Keep references to all reblogs of a status on home feed
When inserting reblog: Add to set of reblogs of this status on
the feed, if original status was present in the feed, add it to
that set as well.
When removing a reblog: Remove it from that set. Take random
remaining item from the set. If one exists, re-insert it into feed,
otherwise do not re-insert anything.
Fix#4210
* When original is removed, toss out reblog references
Eugen Rochko
Matt Jankowski