'Change POU Type To' becomes 'Duplicate as...', avoiding side effects of type change when POU is already instanciated. Also remove leftover returType tag in ex-function POUs, triggering exceptions at build time.

<?xml version='1.0' encoding='utf-8'?>
<BeremizRoot xmlns:xsd="http://www.w3.org/2001/XMLSchema" URI_location="LOCAL://">
  <TargetType/>
</BeremizRoot>