[dashboard] Update Dashboard Testplan and Readme (aces#6632)

Update the Dashboard Testplan to reflect the fact that the widgets found on the Dashboard should be tested on the Modules from which they are provisioned.

Removed everything from the Testplan that I believe to be under the purview of another module.

Also added a small section to the README request which mentions the interaction with other modules through the widget.

    Resolves aces#6467

modules/dashboard/README.md

@@ -32,3 +32,8 @@ Under the _Dashboard_ section of the Configuration module, you can edit 2 settin
 In both the _Projects_ and _Subprojects_ pages of the Configuration module, you can modify (sub)project-specific recruitment targets - these are used in the Project breakdown View in the Dashboard's _Recruitment_ charts panel.   
 
 Note there is currently no relationship enforced between the subproject and parent project recruitment targets -- the former can be larger than the latter. 
+
+## Interactions with LORIS
+
+The dashboard calls upon other modules to supply data to the various "Widget" panels that can be viewed in the dashboard. Without access permission to these modules, a user will not be able to view the respective Widget on the Dashboard. 
+