Caches are now created from an accessor rather than building them in the new(). This allows us to remove the new() and lets people inherit from here however they want to. It also stops us from auto-vivifying a plain hash which causes unintentional object retention.

clear_cache() did not de-reference the hash before clearning which could have caused the same situation of creating an auto-vivified hash.

Regression test put in place to stop this from happening again.