improved database handling for order value evaluation

git-svn-id: https://plugins.svn.wordpress.org/woocommerce-google-adwords-conversion-tracking-tag/trunk@884224 b8457f37-d9ea-0310-8a92-e5e31aec5664
improved database handling for order value evaluation

git-svn-id: https://plugins.svn.wordpress.org/woocommerce-google-adwords-conversion-tracking-tag/trunk@884231 b8457f37-d9ea-0310-8a92-e5e31aec5664