#2 Prompt user for missing menu

[Jim A. Fieser]

A menu needs to be obtained to initialize the site. If a site admin has FTP access to delete the /data/menu.csv file, then they would also be able to re-initialize the site with a different menu. If no menu.csv file exists, prompt the user for a Spreadsheet URL to download. If the same Spreadsheet URL is in that menu, accept it as the new menu.csv. If the URL is not in the menu, inform the user to put it in the menu.