change the way transponder and mode are returned in the response
change the way transponder and mode are returned in the response

previous way used a wrong interpretation of hop-type. in ietf model,
hop-type is reserved for LOOSE or STRICT constraint description.
Instead, transponder info , according to ietf usual way, should be
included aas a new path-route-object type. such object is not yet
defined in IETF so this is a GNPY proposal to use a 'transponder' object
with type and mode attributes.
this is what has been ecncoded in reques.py for requests and for answers

Signed-off-by: EstherLerouzic <9136e9bbec0a09a1685b8ebbe677b6c9b26e8f18@orange.com>

Telecominfraproject/gnpy