#55 add authentication schemes on CallbackHandler

[Charles Lescot]

we should provide a way to add authentiation scheme in callbackhandler (not only HttpCallbackHandler=> abstract class?, refined interface?).

one benefit will eb to add easily custom loginmodule with custom callbacks.

thanks to Libor for this great idea!
http://sourceforge.net/forum/forum.php?thread_id=1658028&forum_id=407993

cheers,

Charles.