Added osgpresentation example as a test bed for new osgPresentation object model.

First cut of example test bed is to test how easy it is to build against Lua, V8 and Python for purposes of running embedded scripts.
Added osgPresentation::Cursor class to wrap up 3D cursor in the scene functionality
Added translucent version of cushion which isn't depth tested to enable one to see the cursor even when it's behind other objects
Removed old cursor code
Removed unused includes
Removed CameraNode reference
Added initial cut of basic scripting support, introducing an osg::Script object to wrap up the individual scripts, osg::ScriptCallback for assigning a Script as node callback and an osg::ScriptEngine base class that plugins implement to provided support for specific scripting languages.

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.
Merge branch 'master' of https://github.com/openscenegraph/osg into Dev