Name Clashes

[zoumaguanxin]

Hi,
In related wiki, the usage of tf_echo is the following:

 tf_echo <source_frame> <target_frame>
 

It is very strange that the result of tf_echo is not consistent with the tf static_transform_publisher published. It confused me long time until I found some notes in this code. In this code, the source_frameid is passed to target_frame argument of lookuptransform function. When source frame and target frame are used to distinct frames, it means that source frame is a moving frame, target frame is fixed. the transform from source frame to target frame is equal to the transform that can transform the point in source frame into target frame. I think tf_echo should keep same convention about frame name with lookuptransform function. This convention is also conformed by robotics.

[tfoote]

Duplicate of #111 #108