JupyterLab support for NNI

[scarlett2018]

Scenario Aiming to facilitate Cloud (Azure, AliCloud, etc.) Linux VM as a data scientist's sandbox environment.
Env: Linux VM with NNI + JupyterLab preinstalled docker
Story: As a data scientist using the above Env, I can embed NNI web UI with JupyterLab within the JupyterLab Tab so that I can have a unique debugging/programming experience inside JupyterLab with NNI.

@liuzhe-lz @weidankong @Johnsonms

reference: https://github.com/chaoleili/jupyterlab_tensorboard

[JunweiSUN]

I think docker is hard to master for data scientists. Also, there may be some port issues if using docker. Can we embed JupyterLab in NNI's package and provide a command to start JupyerLab in NNI's codedir? (Maybe also a magic command in JupyterLab to start an experiment in a notebook.)

[mingaliu]

Yeah, instead of docker, we can have a Jupyter notebook server extension (and some UI nbextension). NNI package can include those extension and we can have the NNI webUI directly render as a tab in notebook?