$.physical.destroy should reparent children

Doing
```JS
var grandparent = Object.create($.physical);
var parent = Object.create(grandparent);
var child = Object.create(parent);
parent.destroy();
```
results in `child{proto}` being `$.garbage`, which will then typically result in it being ejected from it's location, cleaned from `$.pysicals`, and, if it is not otherwise referenced, promptly garbage collected.