A lot of changes. Related to ros#25 ros#15 ros#21 and ros#24.

ros#25 first version of data collector

ros#15 and ros#21 usign a pr2 bag file downloaded from https://projects.csail.mit.edu/stata/downloads.php

ros#24 data collector is already prepared to handle dynamic transforms

src/urdf_parser_py/urdf.py

@@ -7,6 +7,7 @@
 
 xmlr.start_namespace('urdf')
 
+xmlr.add_type('topic_name', xmlr.SimpleElementType('topic', str))
 xmlr.add_type('element_link', xmlr.SimpleElementType('link', str))
 xmlr.add_type('element_xyz', xmlr.SimpleElementType('xyz', 'vector3'))
 
@@ -527,9 +528,8 @@ def __init__(self, horizontal=None, vertical=None):
     xmlr.Element('vertical', RaySpecs, False)
 ])
 
-
 class Sensor(xmlr.Object):
-    def __init__(self, name=None, update_rate=0.0, parent=None, camera=None, ray=None, origin=None, calibration_parent=None, calibration_child=None):
+    def __init__(self, name=None, update_rate=0.0, parent=None, camera=None, ray=None, origin=None, calibration_parent=None, calibration_child=None, topic=None):
         self.aggregate_init()
         self.name = name
         self.parent = parent
@@ -539,6 +539,7 @@ def __init__(self, name=None, update_rate=0.0, parent=None, camera=None, ray=Non
         self.origin = origin
         self.calibration_parent = calibration_parent
         self.calibration_child = calibration_child
+        self.topic = topic
 
     def __get_camera(self):
         """Return the first camera or None."""
@@ -579,6 +580,7 @@ def __set_ray(self, ray):
     xmlr.AggregateElement('ray', Ray),
     xmlr.Element('calibration_parent', 'element_link', False),
     xmlr.Element('calibration_child', 'element_link', False),
+    xmlr.Element('topic', 'topic_name', False),
 
 ])