Add Listo_US_Subdivisions

git-svn-id: https://plugins.svn.wordpress.org/listo/trunk@889914 b8457f37-d9ea-0310-8a92-e5e31aec5664
Introduce listo_list_types filter.

git-svn-id: https://plugins.svn.wordpress.org/listo/trunk@889917 b8457f37-d9ea-0310-8a92-e5e31aec5664