Merging Akka.NET 0.5 into stable master

Includes:

* Initial Fake build support
* Finite State Machine (FSM) support
* GracefulTermination support
* `PipeTo` support
* Stash support
* ActorSystemExtension support
* Full Deployer support
* Full port of Akka TCP remoting layer, minus SSL and secure cookie support; remote deployment and look-ups all work.
* Lots of new specs and additions to the TestKit.