Implemented KROctree class to be used by upcoming occlusion culling and physics features

Refactored scene graph notification system structures to be owned by the KRScene object
Merged Mike's changes

--HG--
extra : convert_revision : svn%3A7752d6cf-9f14-4ad2-affc-04f1e67b81a5/trunk%4082

KREngine/KREngine/Classes/KRDirectionalLight.cpp

@@ -13,7 +13,7 @@
 #import "KRContext.h"
 #import "KRMat4.h"
 
-KRDirectionalLight::KRDirectionalLight(KRContext &context, std::string name) : KRLight(context, name)
+KRDirectionalLight::KRDirectionalLight(KRScene &scene, std::string name) : KRLight(scene, name)
 {
 
 }