Add deprecation warning back for extension shorthands
Add deprecation warning back for extension shorthands

matthiask/feincms2-content,matthiask/django-content-editor,nickburlett/feincms,nickburlett/feincms,mjl/feincms,matthiask/django-content-editor,nickburlett/feincms,joshuajonah/feincms,matthiask/django-content-editor,feincms/feincms,joshuajonah/feincms,matthiask/feincms2-content,michaelkuty/feincms,feincms/feincms,feincms/feincms,nickburlett/feincms,mjl/feincms,joshuajonah/feincms,michaelkuty/feincms,joshuajonah/feincms,matthiask/django-content-editor,michaelkuty/feincms,matthiask/feincms2-content,michaelkuty/feincms,mjl/feincms