Made redirect URLs keep query params

[sdunster]

This commit makes the redirect back to the client app maintain the query arguments that were passed with the original authorise. This is required for a number of apps including the Meteor accounts packages (http://github.com/uowits/meteor-accounts-uow).

The OAuth2 RFC says that OAuth2 providers MUST implement this functionality.
http://tools.ietf.org/html/rfc6749#section-3.1.2

The redirection endpoint URI MUST be an absolute URI as defined by
[RFC3986] Section 4.3. The endpoint URI MAY include an
"application/x-www-form-urlencoded" formatted (per Appendix B) query
component ([RFC3986] Section 3.4), which MUST be retained when adding
additional query parameters. The endpoint URI MUST NOT include a
fragment component.