Added test case for building a complete even model.
	- so far properly adds comments to the response.
Finished test case for building a full event model, for details see the notes in 'PSModelsTests.m.'
Added a 'README.md' to store the data model documentation.
	- Since the source files for CoreDAta objects are auto-generated, any docuumentation would be lost if the model changes and the source files are re-generated.