Bug 20032: Switch single-column templates to Bootstrap grid: Tools

Bug 20032: Switch single-column templates to Bootstrap grid: Tools

This patch updates several single-column Tools templates to
use the Bootstrap grid.

- batchMod-del.tt - Tools -> Batch item deletion -> Submit barcodes or
  item numbers for deletion. The grid is changed for the results and
  confirmation screens.

- batchMod-edit.tt - Tools -> Batch item modification -> Submit barcodes
  or item numbers for modification. The grid is changed for the results
  and confirmation screens.

- koha-news.tt - Tools -> News -> Edit or create a new news item. The
  grid is changed for the edit screen.

- letter.tt - Tools -> Notices and Slips -> Edit or create a notice. The
  grid is changed for the edit screen.

Each of these pages should look correct. The News and Notices page
should have a single centered column with wide margins on either side.
At lower browser widths the margins should disappear.

The batch mod screens should be displayed at full screen width.

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