Only select the original target after a drag.

This allows you to still drag clones around, but when you stop dragging,
the original sprite gets selected.

src/virtual-machine.js

@@ -900,7 +900,7 @@ class VirtualMachine extends EventEmitter {
         if (target) {
             this._dragTarget = null;
             target.stopDrag();
-            this.setEditingTarget(target.id);
+            this.setEditingTarget(target.sprite.clones[0].id);
         }
     }