Refactored codecs to match ZMTP version numbers
Bumped ZMTP revision to 2

* Starting draft ZMTP/2.1 protocol (revision 2)
* Basis for adding security to the wire protocol
* Maintains backward compatibility
Code name clean up
Renamed ZMQ_DELAY_ATTACH_ON_CONNECT_COULD_THIS_BE_ANY_LONGER to ZMQ_IMMEDIATE
Removed pointless comment
More copyright cleanups