don't always show events in systray when notify_on_all_muc_messages is on and trayicon_notification_on_event is off

Make some strings translatable in adhoc commands, Warn user when session id changes in the middle of a session. fixes #3432

use timeout_add_seconds instead of timeout_add (when it's available), more efficient. fixes #3734, #3736

Reverting [9324]. Reopen #3734.

Prevent traceback when gajim-remote is used while gajim is not running. Add a check_gajim_running command to gajim-remote

See #3718. See also [9287].

Merwok complained about left and right arrow on tab in chats couldn't allow him to do traversing. This patch is a almost there fix. What is missing after the new tab is focused, it steals focus [couldn't find how to fix that atm], hopefully Yann remembers nicfit's code better..