mollom 6.x-2.13

Issue #2502961 by eshta, Nick_vh: Remove access to Content Moderation Platform for new users.
Issue #2472407 by eshta, DmitryK: Replace client-side loaded captcha container to prevent nested DOM elements.
Issue #2393595 by eshta, Nick_vh: Provide additional details about test failures for Mollom ping callback.
Issue #2429041 by eshta: Add title to honeypot field for accessibility validation
Issue #2416151 by brunodbo, eshta: Template file not being picked up in custom theme due to invalid filename
Issue #2429789 by eshta: Hide unsupported audio message with standard element-hidden class.
Make sure that tests respects the server url override when testing local endpoints.
Issue #2408771 by eshta: Allow test cases to read endpoints from variables.