- Defaults to today's date. Not really necessary but it's nice.

- This also kind of doubles as documentation of how to run a crowdmatch.
  There are also docs for production, but here the environment variables
  `PGDATA`, `PGDATABASE`, and `PGHOST` need to be set, whereas in prod
  it Just Works (TM) since it's not using a local postgres db.

- Made starting the database (and, more importantly, stopping it)
  conditional (only if not running beforehand) so running crowdmatch
  while the dev server is running won't stop the db in the middle.

  Had to convert `dbmake` to an actual function because calling it in
  the `if` statement there failed with some "No such file or directory"
  error, even though inlining the *exact same command* worked fine.
  Probably some quoting weirdness. Whatever. This is better, anyway.