Arkadiy/proximity warning

[arkadiy-telegin]

Please see https://github.com/arkadiy-telegin/proximity_monitor/blob/master/proximity_monitor/proximity_monitor.py

[missxa]

@arkadiy-telegin

It's a good practice to add a description of added code in a PR. Would be great to have a summary of added features in the future. Also, for the future please work on a separate branch directly in this repo, since now I cannot directly comment on your python file in the fork.

Architecture & design:

• as discussed, it is better to implement a node for a single camera. please change the implementation accordingly. in case more cameras are added to the robot, then launch another node using the camera name for the topic and node names (like you do already)
• publish absolute proximity in meters, not relative_proximity. for the operator meters are much more understandable and it doesn't require knowing that current threshold is

Implementation:

• 10 hz publisher is too low, use 40 hz or higher
• use our established topic naming scheme, i.e. /roboy/pinky/sensing/your/stuff
• call the threshold parameter proximity_warning_threshold (also, it can be potentially different for different cameras)
• set default threshold to 0.2 m in the launch file
• if exception occurs, use node logger's error and not just print

[arkadiy-telegin]

@missxa cleaned up code integrating all the requested changes

[arkadiy-telegin]

@missxa did you have a chance to take a look?