Bug 15959: Use Font Awesome icons for attach item confirmations

 Bug 15959: Use Font Awesome icons for attach item confirmations

When attaching an existing item to a record, the confirmation and error
dialogs should be styled using Font Awesome icons. This patch revises
the buttons and revises the global CSS file.

To test, apply the patch and clear your cache if necessary.

- Locate a record in the catalog to which you can attach an item.
- Select "Attach item" from the "Edit" menu.
- Submit a barcode for an exising item.
- Verify that the confirmation dialog is correctly styled.
  - Test the operation of both the "OK" and the "Attach another item"
    buttons.
- Submit an invalid barcode.
- Verify that the error dialog is correctly styled.
  - Test the operation of both the "OK" and the "Try again"
    buttons.

Signed-off-by: Hector Castro <hector.hecaxmmx@gmail.com>
Works as described

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