Bug 16062 - Remove CSS and images related to old "approve" and "deny" button styles

 Bug 16062 - Remove CSS and images related to old "approve" and "deny" button styles

Now that confirmation dialogs have all been udpated to use Font Awesome
icons, the old CSS for styling "approve" and "deny" buttons can be
removed along with the associated images.

To test, apply the patchs for Bugs 16061 and 16064 if necessary.

- Search the templates for instances of the "approve" or "deny" class
  which don't have a Font Awesome icon associated with it. There should
  be none.
- Confirm that there are no other references to the files "approve.gif"
  and "deny.gif"

Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>