Better module description for associated ("sub") modules

Recommend including "Display Suite" on the description for the associated modules 'Extras' and 'Forms' so that it is clear in the modules UI what these are.

Example:
When uninstalling through Drupal module UI, you must uninstall the subs before DS module. Better description would make it clear that these are the DS sub modules. If one goes back later to "clean up", easy to forget their association.