Bug 27493: Set column width for checkbox only columns

Bug 27493: Set column width for checkbox only columns

This patch updates the global OPAC css such that selectcol type columns
in tables are fixed width at 1ch to ensure these columns do not get
unneccessarily wide.

To test, apply the patch and rebuild the OPAC CSS
(https://wiki.koha-community.org/wiki/Working_with_SCSS_in_the_OPAC_and_staff_client).

Test plan
PAGES: opac-basket, opac-messaging, opac-results, opac-search-history,
opac-suggestions and opac-tags.
1/ Notice that the column containing a checkbox on each of the above
pages is of a mised width, often much larger than required
2/ Apply the patch and rebuild the css file as described above
3/ Notices that the column containing a checkbox on each fo the above
pages is now of a standard, sensible, width.
4/ Signoff

Signed-off-by: Sally <sally.healey@cheshiresharedservices.gov.uk>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>