Unfortunately the Ikano API schema has xs:sequence everywhere, so we need to have most elements in a particular order.
This class solves this problem by extending XML::Simple and overriding sorted_keys to provide the element order for each request.
-IMPORTANT: when using this class, XMLOut must have SuppressEmpty => 1 as an option.
-You will break everything otherwise.
+This is a helper class which should not be used directly. It requires particular options in the constructor (SuppressEmpty) which differ for XMLin and XMLout.
=cut