This cleans up a bit the OCSController/Middleware. Since the 2 versions
of OCS differ a bit. Moved a lot of stuff internal since it is of no
concern to the outside.
The OCSResponse differs from other responses in that it defaults to
XML. However we fell back to json by default.
This makes sure that if nothing is set we don't pass anything.
Which defaults then to the controllers default (which is often 'json')
but in the case of the OCSResponse 'xml'.
