* cleaner get for file based caches
* now db based facts behave like file ones
we now keep local in mem cache to avoid race conditions on expiration during ansible runs
* Add support for no-expiration to jsonfile cache
* Let memcached cache use fact_caching_timeout=0
If fact_cache=memcached and fact_caching_timeout=0
memcached would hit a NameError on _expire_keys