role_of_winning_party field

[mscarey]

The previous role_of_winning_party field is being deleted in #29. It was a fairly simplistic initial effort and apparently it returned wrong answers so often that it was doing more harm than good to the users. However, I think that without it, the users are going to have to look at each case one by one to determine which party is the winner. Probably the name of a party will sometimes be written slightly differently in different parts of the register, so it won't be trivial to match them automatically. I'm opening this issue in case someone wants to try again to categorize winners as "PLAINTIFF", "DEFENDANT", or "N/A". It would be easier to use those categories in queries than to write queries using the party names.