Added configuration page

git-svn-id: https://plugins.svn.wordpress.org/sgr-nextpage-titles/trunk@849531 b8457f37-d9ea-0310-8a92-e5e31aec5664
Minified admin css

git-svn-id: https://plugins.svn.wordpress.org/sgr-nextpage-titles/trunk@849532 b8457f37-d9ea-0310-8a92-e5e31aec5664