Add Operational guide

[mcayanan]

An Inspect Tool Operational guide needs to be added. Initial work was done, but in Word format. It can be obtained by going to the OODT JIRA site:

https://oodt.jpl.nasa.gov/jira/browse/PDS-662

According to @nutjob4life, a lot of open source Python projects are documented at https://readthedocs.org/ (and you can sign in with your GitHub ID and automatically import your projects) and it supports the Sphinx format. Sphinx also lets you use reStructuredText (more common in the Python community) or Markdown (but with limited features).

See also this recommendation for Sphinx for Python: https://python-docs.readthedocs.io/en/latest/writing/documentation.html