Removes and item from this cache based on the given key.
If an entry matching the key is found it is removed from the cache and a
remove event emitted.
No additional checks are done on the item removed. If other systems or parts of your game code
are relying on this item, it is up to you to sever those relationships prior to removing the item.
The unique key of the item to remove from the cache.
This BaseCache object.