[DOC] Add documentation for expert data management

[qjhart]

Our long term goal is to have more rolling cache / update based integragration of the aggie experts. However, we still need to have more developers able to update the current data, both for local development, and for the production system.

We have some existing documention showing how to added harvested users into a dev system #241, but no example use of experts cdl (though the command does have a help page)

I've added a video tutorial that shows the steps I use for updating the production system in the current format. We need a better set of documentation of these seteps for new developers.