Bug 18847 - Add "Save and continue" option to notice editing

Bug 18847 - Add "Save and continue" option to notice editing

This patch adds an option to "Save and continue editing" when editing
notices. The submit button is now a split button in a floating toolbar.
The secondary action of the split button is "Save and continue editing."

To test, apply the patch and go to Tools -> Notices.

- Open any notice for editing. Verify that the toolbar looks correct and
  floats as it should when sections of the form are expanded and the
  page scrolls.
- Edit a notice and click the "Save" button. Confirm that you are
  redirected to the main Notices page and that your changes were saved.
- Edit a notice and click the "Save and continue editing" menu item.
  The page should reload with your updates in place.

Signed-off-by: NickUCKohaCon17 <nicansjr@gmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>