Asynchronous e-mail sending by default

Method signature changed: "MailingListHelper::processQueue" (removed required "&$messages" parameter) "kEmail::send" (removed optional "$immediate_send" parameter) Reborn methods: "EmailTemplateEventHandler::OnProcessEmailQueue" ("email-template:OnProcessEmailQueue" event) into "EmailQueueEventHandler::OnProcessAjax" ("email-queue:OnProcessAjax" event) and "\MailingListHelper::getMessages" "MailingListEventHandler::OnProcessEmailQueue" ("mailing-list:OnProcessEmailQueue" event) into "EmailQueueEventHandler::OnProcess" ("email-queue:OnProcess" event) "MailingListEventHandler::_ensureDefault" into "MailingListHelper::getSetting" Solution for "kEmail::send" method: add optional "$immediate_send" parameter back, but with "null" default value when specified use it as-as during "\kEmailSendingHelper::Deliver" method call restore "EmailTemplateEventHandler::OnProcessEmailQueue" method, but: indicate, that it's deprecated now replace it's body with new code for "MailingListHelper::processQueue" method: restore "$messages" parameter by make it optional when "$messages" parameter isn't specified set it's value from "\MailingListHelper::getMessages" method restore "\MailingListEventHandler::OnProcessEmailQueue" method, but: indicate, that it's deprecated now replace it's body with new code restore "MailingListEventHandler::_ensureDefault" method, but: indicate, that it's deprecated now replace it's body with new code