Add testing using "deferred derivative generation" set

[MarcusBarnes]

From the recent pull-requests from from staff of Discovery Garden Inc. (such as pull-request #124) it has become clear that we have not tested this module when the "deferred derivative generation" setting in Islanodra is on. Task: Add testing when "deferred derivative generation" is set to the testing spreadsheet so that this is adequately tested for future releases of the module against Islandora releases.