Make ParameterizedFunction copy parameter references

In the constructor for a [ParameterizedFunction](https://github.com/holoviz/param/blob/31f5717457b8a53e979f5e5cc5e0c724c69f7f61/param/parameterized.py#L4453), all of the values at the current point in time are copied. Unfortunately, this doesn't copy over references.

#### Is your feature request related to a problem? Please describe.
It's frustrating that I need to add back in all the different previous parameters back.

#### Describe the solution you'd like
I'd like to copy over references, or add a flag to copy them.

#### Describe alternatives you've considered
```python
def instance(fn, **kwargs):
params = fn.param.objects()
params.update(**kwargs)
return obj.instance(**params)
```

Maybe we could make an option to the instance method/