Made significant changes to the textual writeup of the Defining Campaigns vs Threat Actors Idiom
Added Attributed_Threat_Actor layer to make content valid.

Added three Related_Incident refs.
Replaced XML example content with just the snippet from the updated full xml example
workaround for attrib_threat_actor
match inline py with 41b50b
Clean up indenting and XML output
Merge pull request #120 from STIXProject/TA-vs-Campaign-Idiom

threat actor v. campaign idiom: The Sequel