User tutorial data_explorer isn't used

[abachma2]

The 'source/user/tutorial/data_explorer.rst` isn't used anywhere in the website. It's designed to walk a user through how to parse through the output database, which is potentially useful. However, there are several images that are missing from the repo, and it doesn't use cymetric any. Personally, I think there are two options:

1. Redo this page to use cymetric and walk through a sample data analysis
2. Remove this page, and put a note on another page that points to the cymetric repo and the examples there.

Any thoughts?