First pass at creating post-2002 MD results

This finishes a first pass at creating post-2002 Maryland Result
records from RawResult.

* Handle "Other Write-Ins" pseudo-candidate using Candidate.flags
* Batch bulk inserts. This didn't use to be a problem because we
  were just bulk-inserting on a file-by-file basis.  However, since
  we're working from RawResult records, there will be a lot more
  records inserted at once.
* Delete old records before creating new ones.  This still doesn't
  amount to a good atomic strategy, but it mimics the behavior of
  the old pre-rawresult loader.
* Pull the abbreviation from the Party object and use it to set
  Result.party.

Addresses #49