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.
Those are good points, and some guidance/discussion would be good. I'd still vote for not specifying the currency for a couple reasons. First, I suspect we won't actually ever need to compare these values directly to values from another instance. Rather the comparisons would be percentage-based. Also, not enforcing a currency would add some flexibility -- a developing country could use either their local currency, USD, or something else depending on what makes sense to them.