Set the system's default category as the default dropdown category.


git-svn-id: https://plugins.svn.wordpress.org/p2-new-post-categories/trunk@792593 b8457f37-d9ea-0310-8a92-e5e31aec5664
Updating changelog

git-svn-id: https://plugins.svn.wordpress.org/p2-new-post-categories/trunk@793107 b8457f37-d9ea-0310-8a92-e5e31aec5664