Bug 20036: Switch single-column templates to Bootstrap grid: Offline circulation

Bug 20036: Switch single-column templates to Bootstrap grid: Offline circulation

This patch updates three single-column offline circulation templates to
use the Bootstrap grid.

- offline_circ\process_koc.tt - Circulation -> Upload offline
  circulation.

- offline_circ\enqueue_koc.tt - After uploading offline circulation
  file -> Add to offline circulation queue. The confirmation page is the
  page to be tested.

- offline_circ\list.tt - From the confirmation page -> View pending
  offline circulation actions.

Each of these pages should look correct, with a single centered column
with wide margins on either side. At lower browser widths the margins
should disappear.

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>