adjusting download script to include UNFPA, WFP, and UN Habitat; adjuste...

...d process script to factor for new data, address errors and holes in new agency data, and adds country level centroids to activities without locations; also ran new process to get new data

This pull request is the first test of adding UNFPA, WFP, and UN Habitat. This is pulling the latest files from the IATI API. We're factoring for no <location> tags and adding a country-level centroid.  

cc @akshaysinha @abdulriza @Jura