Revert "Convert dropdowns to proper buttons."

This reverts commit 17da848f965115104ae6e00c4e2380051c5c6d98.

Revert to previous navbar, as that's how it's specified in the bootstrap docs.
Remove links to non-existent pages from navbar.
Merge navbar rules.
Use config debug to trigger debug builds with sass, compressors etc.
Refactor to use default bootstrap classes.
Kill override for text-center and properly use the "strong" tag.
Heavy refactor of CSS, use SASS to properly stylize stylesheets.
Stylize dropdown-header when on mobile.
Make navbar JS easier to read and more portable (works also on the brand-new "Coding" menu).
Remove pager.js, as it serves no purpose whatsoever now that paging is done at compile time.
Enlarge ebuild title to make it more visible.
Convert "scripts" kind to coding. Upgrade some logic in the pages_with_sidebar layout, to prepare for a switch out of that schema.
Fix Markdown formatting issues.
Fix missing hover and focus for navbar links.