Add debug tool to follow_wall_angle.

[zbynekwinkler]

This is somewhat raw tool to visualize what follow_wall_angle does. It draws pictures like this:

[m3d]

I understand this PR as draft, i.e. not ready for comments yet ... I do not like much another tool and integration of cv2 into explore.py but ... maybe it is just for current debugging?? i.e. I do not know what is expected from me here? thanks m.

[zbynekwinkler]

I understand this PR as draft, i.e. not ready for comments yet ...

Somehow I was operating with the assumption that a branch without pull request is not ready for comments and draft pull request is ready for comments but it is not considered ready for merge. I realize we have not stated this anywhere yet. Would such interpretation be ok?

I do not like much another tool and integration of cv2 into explore.py but ... maybe it is just for current debugging?

Well, there is currently no way to debug follow_wall_angle and there are also not that many tests for it. That together makes it somewhat hard for me to to trust it. Having visualized how it interprets different scans is helping me gain the trust. I have changed the way the debug stuff is integrated into explore (by using a callback). Maybe it is less offensive now?

I do not know what is expected from me here?

You are doing very well what I expected, thanks. I was expecting some general comments about the direction of this work before I put too much effort into it. I am not sure myself yet where this should land but I still have the feeling there should be a way to visualize what follow_wall_angle is thinking. I am not sure yet "this is it". Any ideas welcomed.