Adding loadersettings free FileManager impl

Starting to remove the giant cyclic dependency that is the `LoaderSettings` from the [BasicFileManager](https://github.com/novoda/ImageLoader/blob/develop/core/src/main/java/com/novoda/imageloader/core/file/BasicFileManager.java)

- This impl also removes the internal thread handling for deleting files from the cache, it should be done from the client rather than hidden.

The class name follows the sytax of `BetterMemoryCache` as I imagine they will all be renamed for the final version
I was following the `BetterMemoryCache` convention and just to be a pain I would have assumed all classes are nonthreaded unless specified :tongue:  `AsyncFileManager` etc