prepare trunk for 9.1

git-svn-id: https://plugins.svn.wordpress.org/comprehensive-google-map-plugin/trunk@997387 b8457f37-d9ea-0310-8a92-e5e31aec5664
update stable tag to v9.1

git-svn-id: https://plugins.svn.wordpress.org/comprehensive-google-map-plugin/trunk@997391 b8457f37-d9ea-0310-8a92-e5e31aec5664