Bug 34412: Inconsistencies in System preferences page titles, breadcrumbs, and header

Bug 34412: Inconsistencies in System preferences page titles, breadcrumbs, and header

This patch makes changes to the markup of various areas of the local use
system preferences template in order to make it more consistent with
other pages in Koha.

To test, apply the patch and go to Administration -> System
preferences -> Local use. View each variation of the page to confirm
that breadcrumb navigation, page title, and page headings are consistent
with each other.

- On the main page confirm that the heading is "Local use system
  preferences"
  - New preference:
    - The form on this page has been updated to make the markup
      structure more consistent with other pages, with the heading
      outside the white box of the form.
    - The two portions of the form have been combined into one so that
      the layout of the form is more consistent with similar forms.
 - Edit preference
 - Delete:
   - The deletion confirmation page has been reformatted to use an
     "alert" style dialog with styled confirmation buttons.
   - The "Data deleted" view has been reformatted to use a "message"
     style dialog.

Signed-off-by: David Cook <dcook@prosentient.com.au>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>