use CWAssert instead of NSCParameterAssert
remove CWErrorSet() and CWErrorSetV()
Over time I have become concerned that I am not using them as much as I thought
I would be, and that they sacrifice some readability of the code over conciseness. So
with that in mind I am removing them for now.
remove corresponding unit tests for now removed api's
refactor CWTask code to not use now removed API's