Fix for the RedirectUrl to handle urls with query params

[zarusz]

For the SignOn flow, when the return url contained an equals (=) sign (e.g. url with query params) it was cut off after the first equals sign.

For example this was my return url: /Auth/SignIn?param1=http%3A%2F%2Flocalhost%3A9000%2F%23%2Fhome

When the SignOn response came in, this library was redirecting to: /Auth/SignIn?param1=

Internally the RelayState was using equals (=) to express key-value pairs, but the value was not escaping any potential equal signs.

Have a look at my unit test.

[zarusz]

@elerch will you consider integrating this pull request?

[elerch]

Merged - thanks for adding the tests!