Add a script to update the popolo JSON schemas

This iterates over the schemas in the schemas/popolo directory and
updates them with the latest version from popoloproject.com.
Update popolo schemas

Update the popolo json schemas with the latest versions from
popoloproject.com.
Initial working version of person merger

Allows merging one person into another person. If there is an
unresolvable conflict then this will return an error, otherwise it will
copy the values over.

Currently this just handles basic fields, still need to add support for
arrays of values.