added uk gift aid; corrected bug that would cause ipn notifications to fail

git-svn-id: https://plugins.svn.wordpress.org/seamless-donations/trunk@854250 b8457f37-d9ea-0310-8a92-e5e31aec5664
tagging version 3.0.0

git-svn-id: https://plugins.svn.wordpress.org/seamless-donations/trunk@854251 b8457f37-d9ea-0310-8a92-e5e31aec5664