Bug 20034: Switch single-column templates to Bootstrap grid: Circulation

Bug 20034: Switch single-column templates to Bootstrap grid: Circulation

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

- circulation-home.tt - Circulation home page. This patch corrects what
  appears to have been a long-broken three-column layout.

- article-requests.tt - Article requests list. Turn on the
  ArticleRequests system preference if necessary. Go to Circulation ->
  Article requests.

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>