Replace main.py with self contained modules

[adam-sedlak]

As is, all modules feed into a single main.py script. This however introduces many inter module dependencies through the imports in main.py. Furthermore, this may not be the most intuitive user-interface as a single run script offers users less behind the scenes control (i.e., one run script does many different actions, reading, writing CSVs, running models, etc.) that are obscured from the user.

Can we replace main.py scripts with module specific methods?

In this manner we would transition to a UI closer to something that of sklearn where each module has predictable well defined methods---such as .train() and .predict(). However how to best do this is an open question. Many modules are related to one another (ACOPF --> SSM --> MOR) and need well defined interfaces to pass data between one another. Additionally some main scripts are across modules. And not all modules share the same methods. A few ideas for how to structure this are

• Instantiation of each module just takes settings. A system object is not a module property and must be constructed separately. In this manner modules only perform actions on a data but do not store data. Storage of data is relegated to the system class.
• Modules have methods like .run(), .write_csv(), and simulate() that accept a system object in their arguments.
• Create a pipeline class to manage inter-module exchanges of data. pipe = Pipeline([ACOPF, SSM, EMT]); pipe.run(). If we can do this in a clean modular way I think it may have potential.

One optional point to consider in this refactor is if we should change some of the import paths to be more user friendly/shorter.