PreviewFrom

chris steipp requested that:

* Can getPostAsHiddenFields in includes/Forms/PreviewForm.php only return a whitelist of fields?

chris steipp mentioned that:

* Checking for PHP_SAPI = 'cli' in includes/Handlers/Forms/MetadataMappingHandler.php seems like
  the wrong way to check if this is running from a job

Change-Id: Id03a741abeea64f0ceae9f8244fe9d92b0fa8bf6