If activity check was enabled in server, the activity check modal wasn't showed
to users and after a given time the user was disconnect, also fix the meeting-end
and error-screen messages, informing the user the reason why he was kicked.

attempt to introduce an additional UserSettings parameter 'bbb_show_public_chat_on_login' as a co-parameter of 'bbb_show_participants_on_login' (the former intended to only have an effect if the latter is 'true')