[Reviewer Keith] Trusted as

Keith

Can you review my changes to authentication.  In summary, we now only authenticate on REGISTER requests. Bono and IBCF are responsible for rejecting anything other than REGISTERs that have not arrived from an authenticated/trusted source, and Sprout will only challenge/authenticate REGISTER requests (anything else that reaches it is accepted).

I've tested live and run the UTs (and fixed up a few that had a broken as a result of this and Andy's change to factor SIP identity in to the authentication checks in Bono).

Mike