Workplane.clone()

I know I can define a function or use `w1.translate((0,0,0))` to create a new reference, but it would be great if there is a simple `clone` method:

```python
w1 = cq.Workplane().box(1,2,3)
w2 = w1.clone()

w2.add(...)
```


```python
    def clone(self: T) -> T:
        return self.newObject([*self.objects])
```
