Fix bug 972533: Enhancements to admin handling of deleted pages.

This adds a new manager to Document, which does not perform any
filtering based on deleted status, and uses that manager for the
admin; this ensures the admin always shows all Documents currently in
the database.

Building on that, the admin filters now include one to show only
deleted Documents.

The admin actions for Document are also updated:

* A new "purge" action is added, to bulk-purge deleted Documents.

* A new "undelete" action is added, to bulk-undelete deleted
  Documents.

* The built-in Django "delete" action is removed, since we want people
  using the standard deletion UI (and because the admin delete action
  bypasses the model delete() method, which is not what we want for
  deleting Documents).
Make selection of links into Quick Links less greedy for toggleable lists.
Fixed anchor is null issue pointed out by @darkwing
Select dir attribute of root element in RTL styles

This commit removes the .html-rtl and .html-ltr classes and updates all
stylesheets to instead select the dir attribute of the root element.
This leaves us with one fewer value to worry about, which will make
certain types of debugging easier.
Work around Stylus @font-face linebreak bug
Merge pull request #2397 from openjck/work-around-stylus-linebreak-bug

Work around Stylus @font-face linebreak bug
Merge pull request #2395 from openjck/select-dir-attribute

Select dir attribute of root element in RTL styles
Localization in progress improvements
Merge pull request #2383 from Elchi3/l10n-inprogress

Localization in progress improvements
Merge pull request #2347 from ubernostrum/deleted-pages-972533

Fix bug 972533: Enhancements to admin handling of deleted pages.
Merge pull request #2394 from riverspirit/promote-mdn-fix-1

Fixed anchor is null issue pointed out by @darkwing
Merge pull request #2393 from JeremiePat/master

Quick Links glitch
fix bug 1010024 - Ajaxify subscribe link
Merge pull request #2392 from darkwing/subscribe-1010024

fix bug 1010024 - Ajaxify subscribe link