Improved Freemarker template exception logging should still backwards compatible ignore exceptions

With HSTTWO-3134 the freemarker template exception logging was much improvement, but for that purpose the default configured freemarker exception handler was switched from "debug" to "rethrow".
This allowed intercepting and better logging of the exceptions, but as a 'side-effect' also caused freemarker to stop processing, while before it silently continued.
This is an not backwards compatible change which isn't needed.
Instead, by creating our own exception handler, which provides the improved exception logging while also using the 'ignore' behavior of continued processing, we can also retain backwards compatibility.