remove old v2.3 files

git-svn-id: https://plugins.svn.wordpress.org/cf-whiteboard/trunk@916966 b8457f37-d9ea-0310-8a92-e5e31aec5664
add new v2.4 files

git-svn-id: https://plugins.svn.wordpress.org/cf-whiteboard/trunk@916967 b8457f37-d9ea-0310-8a92-e5e31aec5664