Implement Camera::ScreenPointToRay() to cleanup raycast code. Implement entity visibility checks and tracking (requires updated Urho3D). Implement GraphicsWorld::IsActive().
Implement GraphicsWorld::FrustumQuery().
Removed redundant nullcheck.
Materials: Implement Mesh component handling asset reference changes. Left few of the Urho related parts open for @cadaver (default empty/error mat apply). New AssetRefListListener: This class moves most of the complexity of managing material requests out of component, atm in particular Mesh. Signals and functions include support for indexes so that the component does not need to loop its local refs all the time to find the correct one. Also beneficial is that the internal state of the list listener can clean and resolve refs without modifying the original Attribute value (hence triggering network change or needs to manage LocalOnly stuff).
Merge remote-tracking branch 'origin/master' into ogre-material