Need public methods to clear cache or clear selected files from it #25

Example: I was trying to download CachedNetworkImage, that required authentication. Forgot to give correct authentication headers (or gave a wrong one). Now cache manager saves as my image an http response - a web page asking to log-in. Code crashes trying to create a JPEG image from that HTML code... There is no official way to remove that bad "image" from the cache until it expires.