4.0.0.beta.2: Fix dropdown focus behavior, minor changes/bug fixes

• Explicitly give toolbox 100% width
• Fix behavior of thumbnails on small screens
• When both :focus and :active applied, prioritize :active
• Remove focus from dropdown checkboxes once the dropdown has been opened
• Changing more styles from the refreshed/mediawiki directory (e.g., move toc styles there)
• Move page indicators
• Improve table of contents and thumbnail styles on small
• Give the header search section overflow:visible (seems to fix issue in Edge where scrollbar appears in the search dropdown on big)

Change-Id: I1d6276b9911a1e75d7365e7861feaba72046a9c9