#32 Contribute SPNEGO (single sign on) support

[Eric Sword]

I have written an Authenticator+Realm to do
Http-Negotiate authentication, either via the standard
Negotiate exchange (SPNEGO/Kerberos) or the older,
MS-specific "WWW-Authenticate NTLM" exchange. This
means that users with browsers that support auto-login
(IE5.5+ by default, Firefox/Mozilla with a preferences
setting) can auto-signin to a web application using
their OS authentication (assuming their machine is
logged into a Windows NT or Active Directory domain.
In theory, it should also work with regular kerberos
authentication on other OSes). The Authenticator falls
back to BASIC authentication if the auto-signin does
not work.

The core classes are implementation independant (i.e.
can compile with no additional 3rd part libraries). I
also have an implementation class that uses the JCIFS
(http://jcifs.samba.org/) and jcifs-ext
(http://sourceforge.net/projects/jcifs-ext/) packages
to do the actual communication with an MS Active
Directory server.

The only change to existing classes are a new entry in
AuthenticatorFactory for the NegotiateAuthenticator.

Would the project be interested in this contribution?
I have a few more changes to make before releasing it.