12179 create Answers table and migrate existing response data to populate it

[DevneyHamilton]

Business planning loads slowly because for over 300 questions and their corresponding answers, Madeline has to extract question and answer data from the database, associate answers with questions, assign required-or-not status to questions based on the loan type, render the question/answer heirarchy into html, and then make javascript adjustments to every question and answer in the browser. The way to reduce loading time is to load fewer questions and answers at once. Loading these questions in smaller portions requires:
Phase 1: replace a single json blob holding all 300+ answers in one database cell with a database table where each answer has its own row (engineering done, needs careful release)
Phase 2: replace an unconventional saving mechanism that can’t be adjusted with conventional Rails form saving (engineering done, needs careful release)
Phase 3: divide the existing credit memo questionnaire such that each top-level section can be saved and loaded separately (engineering in progress). Maintain all legacy data through this change.

This PR represents a 'first phase' of of the three above. In this phase:

• there's a new Answer model and table. An Answer belongs to a response set and question. It stores the answer to that question in that response set. (Response sets, as before, belong to a loan and a question_set).
• there's a 'one time changes' rake task that copies response sets' existing 'custom_data' json blob into a new Answers table
• answer information is read from the Answers table instead of custom_data in response_sets.
• answers coming in from the questionnaire form are saved BOTH to the new Answers table and the custom_data on response sets.

The next phase will involve:

• removing response_sets' custom_data field all together
• removing question's internal_name field
• removing the method_missing override in response_set.rb that handles saving answers from the questionnaire form
• making the questionnaire form work with nested_attributes for answers (probably; if there are issues with this, i may move to json api style in anticipation of phase 3)
• removing Response model; any still needed functionality distributed among response set, question set, question, and answer

Phase 3:

• pending design work, change how questionnaires display and are saved to, mainly so that users can interact with a smaller number of questions & answers at a time, reducing load times and possibly simplifying the front end experience.

Future:
This move to answers table instead of json blob, and accompanying clean up, opens up the possibility for modernizing the form system to have a responsive frontend (e.g. with React) and an API.

[DevneyHamilton]

the previous version of this meant that if one is in a division that inherits question set(s) from ancestor divisions when making a data export, those inherited question sets were skipped.