Incorporate references to legacy datasets; consolidate doc

[JoanneBogart]

Come up with a way to reference datasets not necessarily registered in the system.
Look into existing Confluence page(s) concerning production datasets
Should/can production have a separate root from non-production?

[JoanneBogart]

Closing this issue because the points raised are being discussed elsewhere.
For the first, see issue #104 and associated PR #112
The production db will have a separate root dir. For other dbs, their production subdir will typically be a sym link to the production (or possibly differently named) subdirectory of the production root dir. See some discussion in issue #106.