function handleFileCloseWindow(commandData) {
        return _handleWindowGoingAway(
            commandData,
            function () {
                window.close();
            },
            function () {
                // if fail, tell the app to abort any pending quit operation.
                brackets.app.abortQuit();
            }
        );
    }
Confirms any unsaved changes, then closes the window
@param {Object} command data