Bug 15663: Fix 'remove selected items', add a 'delete batch' button

Bug 15663: Fix 'remove selected items', add a 'delete batch' button

In this patch I have fixed the 'Remove selected items' button.
I have also added a 'Delete batch' button like there is in the Patron Card Creator.

To test:
1) Go to Tools -> Label creator -> New label batch
2) Add 2 items
3) Select the checkbox next to an item you just added and click 'Remove selected items'
4) A pop-up will say that you are yet to select an item. (Please ignore the mistake in the pop-up message, this is being fixed in Bug 15662)
5) Apply patch and refresh. Confirm there is now a 'Delete batch' button in the toolbar
6) Select one item and click 'Remove selected items'
7) Confirm the item is deleted from the batch
8) Select the final item and click 'Remove selected items'
9) Pop-up message will tell you that deleting this item will delete the batch. Click 'Okay'
10) Click 'Delete batch' then 'Okay'
11) Confirm you are redirected to the Labels page and the batch has been deleted.

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

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Brendan Gallagher brendan@bywatersolutions.com
(cherry picked from commit 4bf881d32c41b54357949e4d37b1401b1324bc8e)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>