No Bug: signature utilities - changes to parameter names in prep for skunk classifiers & jsonMDSW

No Bug because this is a tiny incremental step of the larger process of Bug 865791 - only the final pull request for that bug will include the bug number and therefore close the bug when merged.

The future jsonMDSW uses specific field names for the parts that are used to create a signature.  The signature_utilities uses a different set of names for the same data.  This change unifies the names, so that future input from jsonMDSW can just be passed as **kwargs  instead of breaking each piece out and passing them in separately.

This happens now because of the upcoming skunk-classifier system.  Rather than having these new classifiers use the old system and then be rewritten when we adopt the new, I want to make it use the new system from the start.  This will reduce work and headaches later.