Cookie authentication

This is a bit of a monster change...not as bit as Sql Parameters but probably very close.

I have removed all the custom cookie session code. New approach uses ClaimsIdentity and Owin Cookie Auth middleware.

Let me know what you think about this approach. See the Blog Post 5.6 branch for details. Blog post not complete but should have the details at least.
uc1 is auto generated by Visual Studio when you drag a control onto a page. bt would have been better but I was lazy and let VS write some crappy code for me. Maybe we put together some standards for this when we introduce master pages.