Added new runoff PC data from IEC and reorganized the folder structure

This pull request is for the new IEC runoff polling center data. The folder structure has been slightly reorganized (the older data was put into the "first-round" folder) but the real additions are all in the "runoff" folder.

It includes the final output GeoJSON files, the python script to compile the output, and in the "raw" folder: the shell script to download all the new data from IEC and the resulting raw JSON files.

This is ready to merge. Let me know if you have any questions or feedback.

@ianschuler @smit1678