Added new apis to query users and fixed EF.Inmemory
Add error describer

- Follows Resource pattern
- Also cleaned up optional services, by allowing null in constructor
- SignInStatus -> SignInFailure and introduced SignInResult
Cleanup old resources
Sort namespaces, add a unit test
Sort namespace
PR feedback
Public get
Introduce IdentityError

Code is the logical status code for the error
Description is the friendly name