This PR adds a new notification cleaning mode, super perfectly tuned for accessibility, and removes the previous notification cleaning functionality as it's now redundant.

* w.i.p. notif clearing mode

* Better CSS for selected notification and shorter text if Stretch is off

* wip for rebase ~

* all working in notif clearing mode, except the actual removal

* bulk delete route for piggo

* cleaning + refactor. endpoint gives 422 for some reason

* formatting

* use the right route

* fix broken destroy_multiple

* load more notifs after succ cleaning

* satisfy eslint

* Removed CSS for the old notif delete button

* Tabindex=0 is mandatory

In order to make it possible to tab to this element you must have tab index = 0. Removing this violates WCAG and makes it impossible to use the interface without good eyesight and a mouse. So nobody with certain mobility impairments, vision impairments, or brain injuries would be able to use this feature if you don't have tabindex=0

* Corrected aria-label

Previous label implied a different behavior from what actually happens

* aria role localization & made the overlay behave like a checkbox

* checkboxes css and better contrast

* color tuning for the notif overlay

* fanceh checkboxes etc and nice backgrounds

* SHUT UP TRAVIS

* Locale script now accepts overrides and new keys from glitch/locales

* Revert glitchsoc changes to mastodon/locales to prevent future merge conflicts