Opencv_contrib: Restore LineSegmentDetector LSD & avoid license conflict

[ruelj2]

Concerning the removal of LSD due to original code license conflict, it would be a great earning for the community to restore it back by modifying the code in order to avoid license conflict.

The original license conflict issue: https://github.com/opencv/opencv_contrib/issues/2016

Proposal:
Find an alternative way to "Compare doubles by relative error" as in original modules/line_descriptor/include/opencv2/line_descriptor/descriptor.hpp between lines 625 and 824.

[barabanus]

That would be very useful because LSD line detector is very useful and robust.

[ruelj2]

Currently working on it.

[alalek]

Find an alternative way to "Compare doubles by relative error"

This is not enough.
Almost all removed code by mentioned patches has license conflict.

Even derived work from GPL code is not allowed due GPL copyleft license.
Original article should be taken to create code from scratch.

[ParadoxRobotics]

As an alternative, I use the original implementation with a python wrapper
-> https://github.com/xanxys/lsd-python