pathshape cleanups and callbacks

sceneObject:
   UpdateXformChange(mat); operates on the parent object, so made no sense to shove it in void SceneObject::PerformUpdatesForChildren(MatrixF mat){
provide callbacks for when the parent/child relationship changes

simpath+camerapline+pathshape
provide a mechanism to embed a callback for a pathshape defined on a path node. example:

            new Marker() {
               seqNum = "7";
               hitCommand = "TheCommand" // <------------------------------;
               position = "-17.0856 -92.2349 4.00051";
               rotation = "0.0334943 -0.254411 0.966516 179.495";
            };

function PathShapeData::TheCommand(%this,%obj)
{
    echo("Do the thing");
}

Engine/source/scene/simPath.h

@@ -121,6 +121,7 @@ class Marker : public SceneObject
 
 
    U32   mSeqNum;
+   String mHitCommand;
    U32   mSmoothingType;
    U32   mKnotType;