Course of Action API Implementation

PR for #44 

@bworrell , please let me know if anything needs to be rectified. The fields for COA that are not implemented yet are documented as a comment on the issue. I didn't know if you wanted ALL fields done in one pass, or just what is needed for the issue at hand. I assumed the latter.

Also: I had to comment out 3 lines in the bindings.course_of_action.py class; the xmlns:coa attribute was being exported twice into XML. This manner of resolution seems in keeping with other classes that have been translated into APIs.