Consider: support for SecurityIdentifier claims

In CoreCLR and UWP, we need to consider whether or not we will support the use of Windows-isms like the user of SecurityIdentifiers for claims based auth.

In case we decide to, here are the current identified places where this will need to be considered:
- `src/System.Private.ServiceModel/src/System/ServiceModel/Security/IdentityVerifier.cs`
Allows us to use SID/UPN/SPN/DNS claim types and map them as equivalent.