Release 20190116 of the `datalab` command line tool

[yixinshi]

This is a tracking issue for the 20170119 release of the datalab command line tool.

This issue will be used to report the source of the tool, it's changes, and when it is incorporated into the Google Cloud SDK.

The commit of the release is this commit
Fixed bugs:

Race condition when setting up a shim for socket.io #2069
Merged pull requests:

Support datalab connect() to connect a GCE instance created from Deep… #2112 (yixinshi)
Replace Beam with DataFlow since MLToolbox doesn't work with latest beam. #2102 (qimingj)
Separate Py3 package installations in Conda #2100 (qimingj)
Upgrade Protobuf since Apache Beam relies on it. #2099 (qimingj)
Update pip version. #2097 (qimingj)
Add more license files for pip packages installed in conda. #2094 (qimingj)
Add third party license files to container image. #2093 (qimingj)
Update the Drive scopes used by the polymer UI #2084 (ojarjur)
Update pytz and replace google-cloud-dataflow lib with apache-beam[gcp] #2083 (rileyjbauer)
Add an experimental tools directory, including a PoC Datalab manager. #2081 (ojarjur)
Fix Javascript events references #2077 (yebrahim)
Add back jquery-ui dependency #2076 (yebrahim)
Enable Datalab to run in a read-only mode. #2075 (ojarjur)
Ensure that websockets are shimmed before any Jupyter client code runs. #2070 (ojarjur)
Ensure that home directories have the right owner at startup. #2067 (ojarjur)