we can recieve presence before recieving the roster (presence from disconnected transport) so self.connexions[con] must exist for presenceCB.

bugfix : we can recieve messages from offline contacts (invisible or offline stored messages). In thoses cases do not select contact in roster.

bugfix : when a server become unavailable, self.connexions's size changed during process. Now it changes after process.

plugin.connected[account] is a number between 0 and 5 :
  0 offline, 1 online, 2 away, 3 xa, 4 dnd, 5 invisible

so when pressing control+C, exit immediatly

bugfix : when we remove an account that was online, we recieve the status "offline" after the account is removed