Bug 35633: (follow-up) Custom style updates

Bug 35633: (follow-up) Custom style updates

This patch adds custom CSS to the OPAC and staff interface to override
the default style of Chocolat controls (for left arrow, right arrow,
loading, and close window). These controls are given a green color
matching Koha's color scheme.

The bibliographic detail pages in the OPAC and staff interface have been
revised so that the inclusion of Chocolat CSS comes before the inclusion
of Koha's global CSS. We should do this with third-party CSS so that it
can be more easily overridden by ours.

The patch also makes a minor change to chocolat.js to correct a bug. See
commit 6ac89ca8558.

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

- Go to Administration -> System preferences and enable the
  AllowMultipleCovers, OPACLocalCoverImages, and LocalCoverImages
  system preferences.
- Add a local cover image to a bibliographic record:
  - Locate a bibliographic record.
  - From the detail page, click the "Images" tab and then "Upload."
  - Upload an image to attach to the record.
  - Upload another image.
- Return to the bibliographic detail page fro that record, and click the
  image you uploaded.
  - The full-page image viewer should appear, and the controls should
    look correct, with green matching Koha's color scheme:
    - The close button in the upper-right
    - The right-arrow, and then when you click through to the second
      image, the left-arrow.
    - In the footer, the "edit" link should work correctly.
    - Test that the "Full screen" control works too.
- Click the "OPAC view" link to load the record in the OPAC, and perform
  the same tests.

Signed-off-by: Phan Tung Bui <phan-tung.bui@inlibro.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>