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.
What do the prefixes like us_ and og_ mean?