Added support for unihandecode.js

Added support for unihandecode.js on the add page form in the admin.
This support must be explicitly enabled by the user and the django CMS
will not ship a copy of unihandecode.js.
language_chooser fix and docs
Merge remote-tracking branch 'origin/develop' into unihan-slugs
Merge branch 'develop' into unihan-slugs
Updated unihandecode dependency to 1.0.0

Updated the docs to reflect the new layout of unihandecode.js 1.0.0
Added auto-slug for unicode titles to change form
Update docs/upgrade/2.4.rst

Changed typos and the path to get_cms_settings func (in cms, not in django)
Merge pull request #1631 from motiteux/patch-1

Update docs/upgrade/2.4.rst
Merge pull request #1606 from evildmp/language-related-fixes

language_chooser fix and docs
Merge pull request #1605 from ojii/unihan-slugs

Added support for unihandecode.js
2.4 upgrade typos + formatting