Add state transition diagrams for initiator and responder handshakes

[jadamcrain]

From BMK.

We already have the "dot" package integrated and have played with diagram generation.

The transition diagrams will likely need to differ for session oriented (TCP) vs sessionless (serial/UDP). This may perhaps consist of optional transitions / actions in one but not the other.

For instance, in TCP we may want to specify that the connection should be closed for certain reasons, but would never do this for serial.