massive refactor

### Consider this a not-production-ready version of the code

New module (twacsDB.py) added to facilitate the JSON traversal to specific key-value pairs in the instantiation of an object. Each unique key in the JSON payload has a class that specifies the key-path to the corresponding value.

Classic, command-line gnacs usage should be completely consistent. New cmd line option (-D) uses entirely different module for assembling output fields into arbitrary order. Framework is in place to use new module *in place of* twacscsv.py module with very minimal changes needed in post-processing; should be possible to make this replacement soon, after further testing and refinement.