[BugFix] URL was being wrongly decoded when redirecting.

URL was being wrongly URL-decoded when redirecting (e.g. '%2F' in query
string was being decoded to '/'.  The solution is to use Uri.AbsoluteUri
instead of Uri.ToString() - see
http://connect.microsoft.com/VisualStudio/feedback/details/475650/system-uri-constructor-automatically-urldecodes-26-and-3d-to-and