Make session binding optional on authentication

The latest XMPP-3921 specification has removed the session establishment requirement on the initial authentication. Right now Smack will throw an XMPPException if a XMPP server doesn’t include the session feature. Newer servers are not enabling the session feature anymore by default and as such Smack is having troubles establishing initial connections. The code in question is within the SASLAuthentication.bindResourceAndEstablishSession() method.

http://tools.ietf.org/html/draft-ietf-xmpp-3921bis-03