private boolean treeWalk(final Folder root, final Func1<ImmutablePair<ContentStorage.FileInformation, Boolean>, TreeWalkResult> callback) {
        return treeWalk(root, false, callback);
    }
Returns a pair of longs where left one is free space in bytes and right one is number of files
main/src/main/java/cgeo/geocaching/storage/FolderUtils.java