coding style: separate property definitions from each other

While not strictly needed in Python, it's much clearer this way.

Change-Id: I5f8caccde6440cb4032aae5deae577d328834a75

gnpy/tools/service_sheet.py

@@ -121,6 +121,7 @@ class Request_element(Element):
             self.path_bandwidth = 0
 
     uid = property(lambda self: repr(self))
+
     @property
     def pathrequest(self):
         # Default assumption for bidir is False

gnpy/topology/request.py

@@ -140,7 +140,9 @@ class ResultElement(Element):
         # starting implementing reversed properties in case of bidir demand
         if reversed_computed_path is not None:
             self.reversed_computed_path = reversed_computed_path
+
     uid = property(lambda self: repr(self))
+
     @property
     def detailed_path_json(self):
         """ a function that builds path object for normal and blocking cases