Bug 20035: Switch single-column templates to Bootstrap grid: Patron clubs

Bug 20035: Switch single-column templates to Bootstrap grid: Patron clubs

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

- clubs/clubs-add-modify.tt - Tools -> Patron clubs -> New club.
- clubs/templates-add-modify.tt - Tools -> Patron clubs -> New club
  template. Also changed in this file: Markup corrections. Label "for"
  attribute should match the form field's id attribute.

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>