Twenty Fourteen: avoid empty markup when no next or previous image in image template. Props MikeHansenMe and jartes, fixes #26208.

git-svn-id: https://develop.svn.wordpress.org/trunk@26586 602fd350-edb4-49c9-b593-d223f7449a82
Twenty Fourteen: enhance main navigation usability by adding in visual indicators for existence of submenu items. Props binarymoon, iamtakashi. Fixes #26200.

git-svn-id: https://develop.svn.wordpress.org/trunk@26587 602fd350-edb4-49c9-b593-d223f7449a82
wp_list_categories(): Add cat-item-none and cat-item-all classes to the none/all options.

props SergeyBiryukov.
fixes #24428.


git-svn-id: https://develop.svn.wordpress.org/trunk@26588 602fd350-edb4-49c9-b593-d223f7449a82