Initial sketch of bug #282, aggregate cell data export.

I believe this mostly accomplishes the "hourly exports of changes to Cell table" issue, in very broad brush strokes. I haven't managed to test it against S3 live yet and I expect the fields will change some and possibly need preprocessing before export, but I'm posting this for feedback / review now.
Please generate the SQL file for this upgrade (via generate_diff.sh). IIRC there's something weird with the default argument and MySQL (sometimes it needs to be server_default) and the generated SQL generally shows that nicely.