Allow the Items to Display to be all

Problem/Motivation

I have situations where rather than a show more button that shows an additional amount of more results, I want a "show all" button.

Proposed resolution

If the value of the Items to display setting is set to 0, show all results when the "Show more" button is clicked.

Remaining tasks

1. Decide whether the feature is appropriate for this module
2. If approved create merge request
3. Test