Update osi_object.proto

@ThomasNaderBMW 
1. Update the general description.
2. rad/s instead of Rad/s.
3. Counterclockwise is positive and clockwise is negative, not the other way around.
4. No need to mention the use-case of one wheel (e.g.) bicycle, since the sign of the allocated rotational speed is still done with respect to the "vehicle" coordinate system.

Author: Kmeid

osi_object.proto

@@ -501,16 +501,12 @@ message MovingObject
             //
             optional Orientation3d orientation = 7;
 
-            // Rotation of the wheel around the axle.
-            // The wheel frame is the reference system.
+            // Rotation rate in the wheel's frame of reference (rotation around the wheel axle).
             //
-            // Unit: Rad/s.
+            // Unit: rad/s.
             //
-            // Regarding positive or negative values, the right hand rule can be used around
-            // the y-axis of the vehicle frame (helpful: perspective from the mid of the axis). 
-            // Clockwise is positive, counterclockwise negative.
-            // If there is just one wheel centered in the mid of the vehicle frame/axle (e.g. bicycle), 
-            // the wheel is treated as it would be on the "right" side.
+            // The sign convention is defined using the right-hand rule with respect to the vehicle's coordinate system (DIN ISO 8855:2013-11):
+            // Counterclockwise is positive, and clockwise is negative.
             //
             optional double rotation_rate = 8;