Bug 16764: Update printers administration page

Bug 16764: Update printers administration page

This patch updates the template for printers administration according to
current interface guidelines.

- Custom JavaScript form validation is removed in favor of the built-in
  form validation plugin.
- Printer-specific header search form is removed, along with server-side
  pagination code. The functionality of both is now taken care of the
  adding DataTables sorting and pagination to the table.
- Edit and delete links are styled as Boostrap buttons with Font Awesome
  icons.
- Confirmation dialogs are updated to use Font Awesome icons.

To test properly you will need to add multiple printers.

- Apply the patch and open /cgi-bin/koha/admin/printers.pl (there is no
  menu link for the page).
- When no printers exist you should see a message dialog saying so.
- Add a new printer. Confirm that printer name and queue are required
  fields.
- After adding multiple printers, confirm that the table of printers is
  correctly sorted and searched by the DataTables plugin.
- Delete a printer and verify that the confirmation dialog is correctly
  styled.

Signed-off-by: Marc Véron <veron@veron.ch>
Update: rebased and updated Bootstrap 3 classes

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>