add shorthands for constructs classes, for easier notebook plotting

Currently, we have to call utils to plot the objects like trace, geofence, which always calls folium.

However, users might want a `plot` method just like `geopandas.GeoDataframe`:
* `trace.plot()` which is equals to `trace._frame.plot()`
* `geofence.plot()` which is equals to `geofence.geometry`