Fix: added _update_cart_validation to avoid manual override on cart update at checkout. Remove passed=true in validation checks, use the passed parameter instead. Replaced add_error with wc_add_notice."

git-svn-id: https://plugins.svn.wordpress.org/woocommerce-max-quantity/trunk@876904 b8457f37-d9ea-0310-8a92-e5e31aec5664