Bug 36390: Two minor OPAC CSS fixes

Bug 36390: Two minor OPAC CSS fixes

This patch makes corrections to OPAC CSS to address two small issues.

To test, apply the patch and rebuild the OPAC CSS.

- Perform a catalog search which will return multiple results..
- In the table of search results, check the icon and text for the
  controls under each title: "Place hold", "Add tag", "Add to cart" etc.
  - The colors should be consistent, with a slightly darker blue for the
    icons.
- Scroll down until the table header "sticks" to the top of the
  viewport.
- There should be no gap between the header row with the pagination
  links and the row with the "Select all", "Clear all", etc. controls.

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
(cherry picked from commit 09119cf9c51e098db891002035213f250f635077)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>