Added option to create hidden food in hurgermod...

If someone wants to create a food mod for DarkRP that makes use its
DarkRP.createFood function but he doesn't wants this food to be
available to everyone now he just needs to set new last argument called
"hidden" to true, note that this change will not corrupt peoples food
that don't has this new last argument as nil (when no argument is
supplied) and false makes let's it visible, only true hides it.