Deserialize the cache_backend setting into the new settings.CACHES.
Review Request #3580 — Created Nov. 29, 2012 and submitted
Deserialize the cache_backend setting into the new settings.CACHES. Our cache_backend siteconfig setting was being converted into settings.CACHE_BACKENDS, but this isn't compatible with Django 1.4's CACHES, particularly when you want to have more than one cache, as they'd be overwritten. We now specifically deserialize into settings.CACHES['default'], leaving any other backends untouched.
Unit tests pass.
