Move import_billy to use person CDs over memberships
Move import_billy to use person CDs over memberships

... to the person and not the membership. This is because we'll end up
storing information so far over the schema it becomes

mileswwatkins/pupa,datamade/pupa,opencivicdata/pupa,mileswwatkins/pupa,influence-usa/pupa,opencivicdata/pupa,influence-usa/pupa,rshorey/pupa,rshorey/pupa,datamade/pupa