resource: allow optional keys in material resource
resource: allow optional keys in material resource

mikymod/crown,mikymod/crown,galek/crown,dbartolini/crown,taylor001/crown,galek/crown,mikymod/crown,dbartolini/crown,mikymod/crown,galek/crown,galek/crown,dbartolini/crown,taylor001/crown,dbartolini/crown,taylor001/crown,taylor001/crown