Use DataProtectionTokenProvider from DI

Fixes https://github.com/aspnet/Identity/issues/224
Enable and fix Async/Cancellation tests
Add SignInManager CanSignIn

new hook which can be used to block sign in
Fixes https://github.com/aspnet/Identity/issues/129
Reacting to EF naming change
added replace claim functionality. fixes #232

 - added ReplaceClaimAsync method to IUserClaimStore interface
 - implemented ReplaceClaimAsync method from IUserClaimStore inside the
   Microsoft.AspNet.Identity.EntityFramework.UserStore<TUser, TRole,
   TContext, TKey>
 - added ReplaceClaimAsync method to UserManager
 - added UserManager tests for ReplaceClaimAsync method.
 - added some UserStore tests for ReplaceClaimAsync implementation of
   IUserClaimStore