Publishing sonar as sensor_msgs/Range implementation

[ongun-kanat]

This patch implements enhancement in issue #35 also fixes redundancy in #37.
Thanks

[reed-adept]

An alternative would be to have one topic that publishes a set of Range messages, but perhaps that's not how Range is intended to be used? How is Range usually used for multiple instances of the same range sensor? Also would we also need to publish the sonar sensor locations (using tf)?

[ongun-kanat]

Maybe further solution like creating a new message type for sonar messages in RosAria can be better/more flexible. As I see sensor_msgs/Range is used to publish single range data. If we create our own message type we can also publish tf info in it.

[reed-adept]

Using a standard type is best, just wondering what the most typical way of using Range is.

[ongun-kanat]

In the manual (http://docs.ros.org/api/sensor_msgs/html/msg/Range.html) it says it is for single range data. This guy (https://fleshandmachines.wordpress.com/2011/09/16/arduino-double-sonar-with-ros/) also used similar solution. He uses multiple topics for sensor_msgs/Range data.

[ongun-kanat]

I've added missing parts of range message. Tested on Pioneer3DX robot.