GParted_Core::FILESYSTEMS and ::FILESYSTEM_MAP and the methods that
query and manipulate them are self-contained. Therefore move them into
a separate SupportedFileSystems module.
Also having a single class maintaining all FileSystem interface objects
will make testing all the file system types much easier as there will be
no need to duplicate this functionality in the test.
Closes!49 - Add file system interface tests
Mike Fleetwood