Support custom parameters to start-notebook.sh

[danielhollas]

Motivation

In the jupyter-docker-stacks Docs, the proposed solution for HTTPS connection to the notebook is to mount the certificates via volume (this we can already do via custom mounts config 🎉) and passing extra config parameters to the start-notebook.sh commands.

docker run -it --rm -p 8888:8888 \
    -v /some/host/folder:/etc/ssl/notebook \
    jupyter/base-notebook \
    start-notebook.sh \
    --NotebookApp.keyfile=/etc/ssl/notebook/notebook.key \
    --NotebookApp.certfile=/etc/ssl/notebook/notebook.crt

There are other Jupyter config options that might be useful in this way, e.g. setting up a password

https://jupyter-docker-stacks.readthedocs.io/en/latest/using/common.html#jupyter-server-options

Proposal

Add a new configuration option, perhaps titles JUPYTER_SERVER_OPTIONS, by default empty, and pass it on when starting a container.

If this all sound okay to you @csadorf I can take this on.