- MaterialsManager no longer inherits from ResourcesManager. This has been done because MaterialsManager won't allow to modify more than one material at the same time, so the overloading of having selections of materials isn't necessary.
- Now MaterialsManager inherits from ServerWritter, Observer and Observable classes.
- Removed unused methods and includes from MaterialsManager class.
- Now MaterialsManager::selectMaterial() returns a MaterialHandlerPtr.