Changed subject from string to ClaimsPrincipal in IUserService
Merge branch 'dev' of https://github.com/thinktecture/Thinktecture.IdentityServer.v3 into UserServiceRework
Added .User property to AuthenticateResult
Added new ctors for auth result
rework AuthenticateExternal with the new AuthenticationResult changes
Merge branch 'UserServiceRework' into dev