[WIP] simpler BoundingBox2D (ros-perception#5)

* Bounding boxes: Switch back to center instead of origin

* BoundingBox2D: use floats for size

* Add pixel/meter warning to BoundingBox2D

* Use RegionOfInterest instead of BoundingBox2D

msg/BoundingBox2D.msg

@@ -1,9 +1,10 @@
-# Note: This message plans to move to geometry_msgs in the final implementation.
+# Note: This message *DOES NOT* plan to move to geometry_msgs in the final
+# implementation, because it uses pixels, not meters.
 
-# The 2D position (in pixels) and orientation of the bounding box origin.
-geometry_msgs/Pose2D origin
+# The 2D position (in pixels) and orientation of the bounding box center.
+geometry_msgs/Pose2D center
 
-# The size (in pixels) of the bounding box surrounding the object relative
-# to the pose of its origin
-uint32 size_x
-uint32 size_y
+# The size (in pixels) of the bounding box surrounding the object relative 
+# to the pose of its center
+float size_x
+float size_y

msg/BoundingBox3D.msg

@@ -1,8 +1,8 @@
 # Note: This message plans to move to geometry_msgs in the final implementation.
 
-# The 3D position and orientation of the bounding box origin
-geometry_msgs/Pose origin
+# The 3D position and orientation of the bounding box center
+geometry_msgs/Pose center
 
-# The size of the bounding box surrounding the object relative to the pose of
-# its origin
+# The size of the bounding box surrounding the object relative to the pose of 
+# its center
 geometry_msgs/Vector3 size

msg/Detection2D.msg

@@ -9,9 +9,8 @@ Header header
 # Class probabilities
 ObjectHypothesisWithPose[] results
 
-# A 2D bounding box surrounding the object, specified in the coordinates of the
-#   original input image.
-BoundingBox2D bbox
+# 2D bounding box surrounding the object.
+sensor_msgs/RegionOfInterest bbox
 
 # The 2D data that generated these results (i.e. region proposal cropped out of
 #   the image). Not required for all use cases, so it may be empty.