Update to official 2.0 release of Microsoft.AspNet.Identity.Core

- Implement new email confirmation, update tests
- Remove IUserConfirmationStore, not in RTM
Implement new PhoneNumber & PhoneNumberConfirmed.
- While I thought it would be nice to track when the confirmation happened, that's not the direction the EF implementation is going so to keep things similar I'm just going to stick with bools for confirms and mirror some of what EF does to lower the barrier to using this (since it's supposed to be about drop in and go with little effort), plus YAGNI
Implement IUserTwoFactorStore