Added ExternalNode to represent other endpoints communicating with the system under test.
Added sample ST project to demonstrate external nodes
Added a couple sample tests for external nodes
Added another sample test

Demonstrates sending from the system under test to an ExternalNode.  Removed the need to hard-code the URI between the actual SUT and the ExternalNodes, but it needs to be baked in.
Added syncing between in-memory channel URIs when testing
Removed unused code from ExternalNode
Merge pull request #173 from DarthFubuMVC/externalNodes

External nodes