render: effectively rename Display to Output, push remaining common code into Renderer task

src/animations.rs

@@ -64,7 +64,7 @@ impl Shader for GayBarberShader {
 }
 
 impl<T: Surface> IdleTask<T> {
-    pub fn new<S: Surfaces<T>>(surfaces: &mut S) -> Self {
+    pub fn new<S: Surfaces<Surface = T>>(surfaces: &mut S) -> Self {
         IdleTask {
             solid: surfaces.new_surface(&Rectangle::everything()).unwrap(),
             surface: surfaces.new_surface(&Rectangle::everything()).unwrap(),