Migration to delete member folders for nonexistent members

[ejucovy]

e.g. Krisnoticias on openfsm

It would be nice to export a snapshot of the member folder's contents just in case it's ever needed again.

Would find these members by iterating over the app.openplans.people folder and checking the corresponding ID on the app.openplans.portal_memberdata folder.

Would also be a good idea to then query portal_catalog and membrane_tool for that ID and clear out anything that's still in there.