MessageTemplate::sendTemplate() - Accept `array $messsageTemplate` option

MessageTemplate::sendTemplate() - Accept `array $messsageTemplate` option

When using `sendTemplate()`, how does it resolve the literal content of the template?

* (Before+After) You may give `string $valueName` (identify+load template by workflow-name)
* (Before+After) You may give `int $messageTemplateID` (identify+load template by ID)
* (Before+After) You may give `string $subject` (override the msg_subject)
* (After) You may give `array $messageTemplate` (specify the content for any/all fields;
  eg msg_subject, msg_text, msg_html)
* (After) Using `string $subject` is deprecated