React to DI changes
Adding type constraint on IdentityBuilder.AddService
Merge branch 'release' into dev
Use stronger password hashing algorithms by default.
New defaults:
Alg: PBKDF2
PRF: HMAC-SHA256
Iter count: 10,000
Salt size: 128 bits
Subkey size: 256 bits
Fix samples typo
Use DataProtectionTokenProvider from DI

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

Used to block sign ins for things like unconfirmed users