Changes and upgrades in version 8.15

Changes and upgrades in version 8.15

fixed autoresponder and form id conflict on landing page's javascript.
updated mail merging function to include landing page url in autoresponder and broadcast messages.
copied the landing page feature to the autoresponder module. Instead of the landing page being managed through the product feature, you can now manage and create multiple landing pages through the autoresponder module.
implemented landing page cloning feature.