changed file name, method name, settings slug and options name

git-svn-id: https://plugins.svn.wordpress.org/readykommerce-multi-newsletter-signup-light/trunk@857243 b8457f37-d9ea-0310-8a92-e5e31aec5664
added changed log

git-svn-id: https://plugins.svn.wordpress.org/readykommerce-multi-newsletter-signup-light/trunk@857244 b8457f37-d9ea-0310-8a92-e5e31aec5664
fixed changed log message

git-svn-id: https://plugins.svn.wordpress.org/readykommerce-multi-newsletter-signup-light/trunk@857245 b8457f37-d9ea-0310-8a92-e5e31aec5664
fixed changelog and upgrade notice

git-svn-id: https://plugins.svn.wordpress.org/readykommerce-multi-newsletter-signup-light/trunk@857252 b8457f37-d9ea-0310-8a92-e5e31aec5664