enable clear_graphics and run_callbacks agin

update plugin signature to recieve bevy structs, add Arc<Mutex<>> around gfx_components, we we can get shared mutable access
add prefab_meshes() access function

Remove Arc<Mutex<>>

src_testbed/objects/node.rs

@@ -17,6 +17,7 @@ use {
     rapier::geometry::{Ball, Cuboid},
 };
 
+#[derive(Clone, Debug)]
 pub struct EntityWithGraphics {
     pub entity: Entity,
     pub color: Point3<f32>,