Add a normalize_cache_backend function.
Review Request #3604 — Created Dec. 1, 2012 and submitted
Add a normalize_cache_backend function. This provides a function for taking either a new-style CACHES dictionary or an old-style CACHE_BACKEND and returning a valid CACHES dictionary. It's basically just logic moved out of siteconfig and into a new djblets.util.cache. Now that we have this file, I'll later begin work on transitioning our other caching functions.
Unit tests pass. Tested this with my new cache support in RB.