hook up display system

Can we by default have python jlwrap objects be hooked up to the display system?
[It should just be a matter of overloading the correct _repr_ methods](https://ipython.readthedocs.io/en/stable/config/integrating.html).
E.g. just attach these defitions to the python object:
```python
def _repr_html_(self):
return Main.repr(Main.eval('MIME"image/png"()'), self)
```
Or something like this ;)