Add addBookmark and removeBookmark methods

These add and remove conference bookmarks only (which are really the
only ones ever used..)
Re-enable using the old WebSocket protocol.

Set the transport to 'old-websocket'. Manual configuration of wsURL is
required for this transport.
Track joined MUC rooms.

muc:join -> You joined the room
muc:leave -> You left the room
muc:available -> Any MUC related available presence
muc:unavailable -> Any MUC related unavailable presence
Emit plain JSON in events instead of JXT objects.
Update dependencies
5.0.0