Bug 36864: Add classes/CSS/fix markup on request.tt

Bug 36864: Add classes/CSS/fix markup on request.tt

To test:
1. APPLY PATCH
2. Regenerate CSS ( https://wiki.koha-community.org/wiki/Working_with_SCSS_in_the_OPAC_and_staff_interface )
3. Place a hold
4. On reserve/request.pl the 'Hold a specific item' fieldset should be
   disabled by default.
5. While disabled try clicking on the Allowed pickup locations
   dropdowns, you should not be able to.
6. In the 'Hold next available item', while enabled, you should be able
   to interact with the dropdowns.
7. Use the radio buttons to enable the 'Hold a specific item' fieldset.
   You should now be able to interact with the dropdowns.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>