Port WCF message security to Core

[blowdart]

For full WCF support, and compatibility with Mono, WCF needs to bring in Message Security and the myriad of supporting classes around it.

Message security enables confidentially, integrity and authentication within the message, rather than relying on the transport, thus enabling end-to-end security through message routers and a wider set of authentication mechanisms which are not limited by transport capabilities.

[StephenBonikowsky]

Looks like a duplicate #3755