Bug 20045: Switch single-column templates to Bootstrap grid: Various

Bug 20045: Switch single-column templates to Bootstrap grid: Various

This patch updates various unrelated templates to use the Bootstrap
grid.

- about.tt - The about page
- auth.tt - The login page

  These pages should look correct.

- reports/reports-home.tt - The reports home page
- admin/admin-home.tt - The administration home page

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

- serials/subscription-add.tt - Serials -> Add subscription. The entry
  form should look correct during each step of the add/edit process.

- suggestion/suggestion.tt - Acquisitions -> Suggestions -> New
  suggestion. The page with the new suggestion form should look correct.

Signed-off-by: Roch D'Amour <roch.damour@inlibro.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>