[ticket/12662] Initial setup

PHPBB3-12662
[ticket/12662] Enable responsive linkslist for IE8

Also fixed arrow color

PHPBB3-12662
[ticket/12662] RTL (bidi.css) fixes

PHPBB3-12662
[ticket/12662] Fix rounding problems when detecting relative height

Firefox and IE round subpixels up, while webkit rounds down. So we have
to account for that.

PHPBB3-12662
[ticket/12662] Improve icons and footer links

PHPBB3-12662
[ticket/12662] Added ARIA functionality

PHPBB3-12662
[ticket/12662] Improve template checks

And changed _CLEAN to _SIMPLE, and move teamlink events

PHPBB3-12662
[ticket/12662] Update PR after ticket/12553 merge

Rebasing was a nightmare with all the code moving around between
commits. Hopefully this will merge without a rebase.

PHPBB3-12662