Fix netcat, pin tornado 4.x for R + zmq issues, update various R libs

Disable datascience-notebook precompilation

Add netcat

Add pyarrow installation

sparklyr add to r-notebook

Netcat (nc) is often used as a tool to test socket server/client, 
and very useful to quickly get started with, f. e., Spark Streaming. 

See #583.

Update to Toree 0.2.0 RC3

sparklyr alone without any other spark package added to the install image.

This way we can profit from pandas UDF

Add jupyterlab_bokeh extension

Chown of home dir needs to be recursive

add r-htmltools pkg

Without the extension it is not possible to use all Bokeh functionalities in JupyterLab

Add instructions for enabling Jupyter Lab interface with OpenShift deployment.

Spark 2.3

Avoid placing anything under home directory in OpenShift deployments.

Add entries to passwd/group if running as user not in passwd file.

Sample builder scripts for build custom notebook images using Source-to-Image.

Avoid placing anything under home directory in OpenShift deployment example so can use it to mount volumes.