plugin XEP-0045: fixed joining workflow: - room keep joining workflow state, and display warning when something is received at unexpected moment - state is change immediatly when subject is received (which must be the last thing before live messages), avoiding timing issue if history storage in database is taking too much time - user joined/left data are not saved anymore in history as it takes a lot of space for little interest. A future option may allow to re-enable it if needed.