Download single bag files when running samples from apt

[Affonso-Gui]

When trying to run this sample, I got the following error:

[FATAL] [1653975595.871342887] [/rosbag_play]: Error opening file: /opt/ros/melodic/share/jsk_perception/sample/data/2019-07-18-15-37-50_pr2_self_see.bag
[rosbag_play-2] process has died [pid 3785, exit code 1, cmd /opt/ros/melodic/lib/rosbag/play /opt/ros/melodic/share/jsk_perception/sample/data/2019-07-18-15-37-50_pr2_self_see.bag --clock --loop __name:=rosbag_play __log:=/home/affonso/.ros/log/16a3703a-e0a4-11ec-a4b5-b0359fc03d25/rosbag_play-2.log].
log file: /home/affonso/.ros/log/16a3703a-e0a4-11ec-a4b5-b0359fc03d25/rosbag_play-2*.log

This is because the bag files are only downloaded when compiling the package from source.
Needless to say, this is not very friendly to users trying to run samples from the apt installation.

How about we set an on-demand dowload_sample_bag script as follows, and pass the downloaded file as a roslaunch argument?

rosrun jsk_perception dowload_sample_bag 2019-07-18-15-37-50_pr2_self_see.bag
roslaunch jsk_perception sample_robot_to_mask_image.launch bag_file:=2019-07-18-15-37-50_pr2_self_see.bag

@708yamaguchi
@iory