Add script to produce FeatureCollection files per state and type of district

[alexanderankin]

The script produces a FeatureCollection type of GeoJSON file which contains all the information in individual feature files representing individual districts. While the individual files system is a good way to organize information as an ultimate source-of-truth, the files this script produces are useful for gaining a big-picture perspective on the data. This script produces such files where applicable, is readable, and works rather quickly.

I have on my fork also a branch with the files it generates committed in case the maintainers of this repository find this to be an agreeable proposition. What do you guys think?