Updating base and python docker files to fix issues with jupyterlab extensions

In one of the previous updates, some jupyterlab extensions (ipympl and itkwidgets) stopped working due to incompatibilities between some package versions. In this MR this is fixed. As usual, other packages were updated to their latest version.

Note that the image includes an alpha version of itkwidgets 1.0, because the previous versions are incompatible with jupyterlab>3 (see https://github.com/InsightSoftwareConsortium/itkwidgets/issues/405).

In addition, installing ipywidgets in the base environment, as recommended here: https://ipywidgets.readthedocs.io/en/7.x/user_install.html#installing-in-jupyterlab-3-0