4.0.0 beta.1: Add messages to i18n files, misc. improvements

• Fix width of site navigation buttons for a single wiki
• List default en and qqq translations in i18n files
• Add more spacing below page tools/user tools headings in toolbox dropdown
• Add mixin to disable the sticky toolbox behavior. In so doing, remove references to the .box-shadow mixin from mediawiki,mixins.less. Any browsers that benefit from the mixin are very out of date, and it makes things easier because then mixins in mixins-public.less can use box-shadow (since items in mixins-public.less can't rely on any files from ResourceLoader, but the skin doesn't rely on ResourceLoader for box shadows anymore).
• Other misc. tweaks to make using the template easier

Change-Id: I92c6a69be3af8ec645cc2f4d6056e2b1fc884d92