Problem: Documentation does not specify how to upgrade if several versions behind the current release #316
Description
The Upgrading documentation does not give the advice that we recommend upgrading one version at a time (e.g. From AtoM 2.7 to 2.8 and from 2.8 to 2.9). rather than skipping over major version (e.g. 2.6 to 2.9).
It would be useful to clarify this advice in the upgrading docs to reduce community upgrade issues.