[FIX] Cloning conference menu
[FIX] Cloning conference menu

	- entries in conference menu are now cloned properly
	- method 'clone' added to 'SystemLink' class
	- fix#414
	- reviewed by jbenito: small fixes.

DirkHoffmann/indico,OmeGak/indico,mic4ael/indico,ThiefMaster/indico,mic4ael/indico,DirkHoffmann/indico,indico/indico,DirkHoffmann/indico,pferreir/indico,mvidalgarcia/indico,pferreir/indico,ThiefMaster/indico,ThiefMaster/indico,mic4ael/indico,indico/indico,pferreir/indico,pferreir/indico,indico/indico,DirkHoffmann/indico,mvidalgarcia/indico,OmeGak/indico,mvidalgarcia/indico,OmeGak/indico,mic4ael/indico,indico/indico,OmeGak/indico,mvidalgarcia/indico,ThiefMaster/indico