Replies, reactions, and contact details

* Rich replies, including reply to image and reply with image
  (For editable quote, do copy message + paste as quote now)
* Replies of only a single emoji send a reaction to supporting clients
  (Retract message to remove reaction)
* Display incoming reactions as replies (better UI later)
* Swipe to reply
* Reply with a new thread to "fork" a thread, original message will be included
  in the "single thread view"
* Adding a contact to roster from system contacts preserves name and tags
* Fetch and render vcard4 on Contact Details
* Fix "Failed to inflate ..." warnings (thanks Hugh Daschbach!)
* Fix changing custom theme colour repeatedly getting stuck (thanks Hugh Daschbach!)
* Ping all online MUCs very occasionally, in case they got disconnected
* Allow experimental prefix/suffix labels in Command UI forms
* Respect tag visibility setting everywhere
* Fix for command bar "flickering"
* Several crashing bug fixes