function getParentPath(fullPath) {
        if (fullPath === "/") {
            return "";
        }
        return fullPath.substring(0, fullPath.lastIndexOf("/", fullPath.length - 2) + 1);
    }
Get the parent folder of the given file/folder path. Differs from getDirectoryPath() when 'fullPath'
is a directory itself: returns its parent instead of the original path. (Note: if you already have a
FileSystemEntry, it's faster to use entry.parentPath instead).
@param {string} fullPath full path to a file or directory
@return {string} Path of containing folder (including trailing "/"); or "" if path was the root