Issue #8: implement feedback from klaasvw@Codelab42*CrossCheck: "includes shouldn't be in a directory called files". Also implements "check if there are no contrib alternatives for exporting panelizer php code" -> Export now makes use of the Panels & CTools API.
Issue #8: implement feedback from klaasvw@Codelab42*CrossCheck: "use the same method as the node migration for importing PHP code instead of defining an intermediary XML format"