Bug 17039: Adding 'cancel' link and 'add new item' button to item edit form

Bug 17039: Adding 'cancel' link and 'add new item' button to item edit form

To test:
1) Go the the detail page for a record on staff side
2) Edit an existing item and scroll down to Save button
3) Notice no easy way to add a new item or cancel out of the form
4) Apply patch and refresh page
5) You should now see a new button next to the Save button, 'Add a new
item', and a link 'Cancel'
6) Confirm clicking Cancel takes you back to the detail page for the
record
7) Go to edit an item again
8) Change some fields/add some info to the item
9) Click the 'Add a new item' button and a confirm box should pop up.
10) Confirm that clicking 'cancel' does NOT take you to a new page, and
your changes are still there
11) Click the button again, and this time click 'OK'
12) Confirm you are redirected to the 'add item' form

Sponsored-by: Catalyst IT
Signed-off-by: Hugo Agud <hagud@orex.es>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>