Changes how rich message markup is generated and kept track of.
We now have a MessageText class which subclasses String and which keeps
track of the rich markup associated with the message.
- Declaratively render the emoji picker dropup
- Got rid of converse-emoji-views
- Adapt OMEMO to the new buttons stuff
- Make emojis json global, to try and speed up tests
- omemo: Move functions to the top of the module