Authentication attributes.
Login handler. For now login URL is hardcoded to /login.

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extra : amend_source : 46be2a9109e1a2b6ae26c47b22886cb3312cf9cf
Merge
Allow multiple exception handlers.
Use default error messages in demo app.
Location: header should be absolute per RFC 2616 para 14.30. Enforce this.
Handle query and fragment.
Make the login URL configurable.

--HG--
extra : amend_source : da22b9dee6b940c9b977e5732cbf5313991273b4
A couple of fixes.