Indicators configuration

This adds models to store the transit indicators configuration based on the wireframes (I checked the functional spec as well but wasn't able to find any others). The configuration includes:
- local poverty line
- buffer distance
- maximum allowable commute time
- maximum allowable walk time (these last two are for the job indicators travelshed).
In addition, peak travel times exist as a separate model since there could be more than one of them.
Should this really be in USD, or does local currency make more sense? I'd think people would want to input this using their local currency, and the demographic information would also be in their local currency.