To the Lua plugin added support for assigned lua functions to C++ osg::Objects via the new osg::CallbackObject mechanism. To invoke the scripts function from C++ one must get the CallbackObject and call run on it.
Renamed ScriptCallback to ScriptNodeCallback to avoid possibly confusion between osg::CallbackObject and the ScriptNodeCallback.
Provided are lua, python and V8 (for javascript) plugins that just open up enough of a link to the respective libs to run a script, there is no scene graph <-> script communication in current implementation.