Upgrade slick to 2.1.0

Also contains some starts to refactors. Making this PR now as to match up with the upgrade to slick 2.1.0 in GeoTrellis and the gtfs-parser project.

Feel free to ask questions about the work-in-progress refactor on this PR. I'm making comments to point out a couple of things that I changed.
Cool. We want to load all of the IndicatorCalculators that exist in the indicators directory. There will eventually be around 25 of them. Do you know how to do this with reflection? I've done similar things in C#, but wasn't able to figure out how to do so here.