Bug 28242: added captions to tables and legends to forms

Bug 28242: added captions to tables and legends to forms

Ensured that in the OPAC, all tables have relevant captions and all forms have relevant legends.

Many of these have class="sr-only" so they are not visible but will be
available for people who use screen-readers.

To test:
1) Go to OPAC
2) Apply patch and dependencies
3) Check that on all pages, any tables have a caption (many of them will
    not be visible, but will be in the markup code)
4) Check that on all pages, any forms have a legend (many of them will
    not be visible, but will be in the markup code)
5) Check that the captions are appropriate and relevant
6) Check that the legends are appropriate and relevant

Sponsored-by: Catalyst IT
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>