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
if bettermemorycache jumped off a cliff would you follow?

Yeah I know the name I gave was rubbish but I was trying to point out name the class after the implementation :+1: