Density doesn't consider physical barriers

[bettinardi]

Density measures should consider physical barriers like rivers, railroads and interstates. The internal density calculations in the ABM and similar should consider getting updated from "as the bird fly's" distance - https://github.com/RSGInc/SOABM/blob/master/template/scripts/SOABM.py#L591

To instead using the network to better represent the distance between zones.