exec.launch command line video debug option

[javatechs]

Option added to exec.launch to conditionally launch debug video.
Parameters:
vid: display video debug
Example:
roslaunch robo_magellan exec.launch vid:=true
vs
roslaunch robo_magellan exec.launch

@pryme, please test.

e743809

[pryme]

@javatechs This works on Victoria, assuming the user launched an SSH -X session. If no -X then the following error is generated, although this did not kill ROS in my test. Error is no -X : [image_view-19] process has died [pid 16817, exit code -6, cmd /opt/ros/kinetic/lib/image_view/image_view image:=/cone_finder/colorImage __name:=image_view __log:=/home/robot/.ros/log/01e56f4c-18ca-11e7-bfcc-0007323c4b8f/image_view-19.log]. log file: /home/robot/.ros/log/01e56f4c-18ca-11e7-bfcc-0007323c4b8f/image_view-19*.log