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/KRSkyBox.cpp

@@ -14,7 +14,7 @@
 #import "KRMat4.h"
 #import "KRResource.h"
 
-KRSkyBox::KRSkyBox(KRContext &context, std::string name) : KRNode(context, name)
+KRSkyBox::KRSkyBox(KRScene &scene, std::string name) : KRNode(scene, name)
 {
     m_frontTexture = "";
     m_backTexture = "";