Provide a way to disable animations for a11y

Problem

With all the shiny new frontend stuff we're exposing users to, there are more animated elements on pages. Those animations can cause motion sickness reactions on some people. See child issues.

For those curious here is an article from the guardian about ios issues and some more details from wikipedia's motion sickness page.

a11y is a core gate, we have to find a suitable solution that allows us to remove/reduce all animations in core and contrib. I'll paste text from a reply of Charles Belov in the tour animation issue:

In my mind it would be part of core, just as the iPhone offers a "Minimize animation" setting in its native settings. The idea is that Drupal 8 will be accessible out of the box.

The other advantage of putting it in core - aside from Tour being accessible out of the box - would be that it would encourage contibs that utilize animation to query that setting and respect it. If Minimize Animation was in and of itself a contrib, that would greatly reduce the likelihood of other contribs querying it.

Proposed solution

The plan is to add a sitewide and user-level setting to toggle animations. This setting will do:

1. jQuery.fx.off = true;
2. Add no-animate.css file containing: .no-animate * {transition:none !important}
3. There will be a new setting available for core and contrib JS: drupalSettings.noAnimate. That way code can do if (drupalSettings.noAnimate) {} directly and we don't have to add this when animations are on (which is by default).