Consider extra helpers / project syncs

[stucka]

We probably should have a small helper program distributed with the bln-python-client that allows a one-line download. "Here's my directory, here's my project name or project ID, download all the updates." BLN project response includes an MD5 hash, modified time and file size we could use to determine what needs to be updated. A CRC32c hash is theoretically available but not returned in the response; see https://github.com/biglocalnews/biglocalnews.org/issues/644