Show_all function on widget

Feature request

I think it would be very useful to have a simple function widget.show_all(), which prints a table with all available rpc methods and the first sentence of the docstring what they actually do. This would allow users to find the respective method quickly, and they can check the docstrings in more detail on the methods for explicit usage.

Expected behavior

This could be automatically created for all widgets. Below would be the expected behaviour for the BECImageShow

dock = gui.panels["docks"]
fig = dock.widget_list[0]
im = fig.add_image("eiger")
im.show_all()
| Function           | Description                      |
|--------------------|----------------------------------|
| set_autorange      | Set the autoscale of the image   |
| set_vrange         | Set the range of the color bar   |
| set_color_map      | Set the colormap of the image    |
| add_custom_image   |                                  |

FYI: add_custom_image is missing a docstring. Just found it.