[Engine-XMPP] detect facebook and prevent facebook bugs
[Engine-XMPP] do not "update" PersonChat name if IdentityName didn't change

there is no update function for chats -> remove and recreate is not very nice, prevent it wherever possible
[Engine-XMPP] display "is now known as" message on IdentityName change
[Engine-XMPP] prevent duplicate printing of status update

some xmpp clients and servers create duplicate presence updates