ft: refactor materials/texture decoupling

made it so all materials can use a texture for colour source. this
should be extendable if we want to do e.g. coded patterns in future

src/main.rs

@@ -27,10 +27,8 @@ fn main() {
     if args.len() > 1 {
         json_file = &args[1];
     }
-    println!("we done serializingiaonosnl");
 
     let json_str = fs::read_to_string(json_file).expect("Reading specified scene file failed!");
     let mut scene: Scene = serde_json::from_str(&json_str).unwrap();
-    let mut scene: Scene = Scene::random();
     render(&mut scene);
 }