Restore LineSegmentDetector LSD & avoid license conflict

[jeanchristopheruel]

Relative to #2524
Original issue with license conflict: #2016

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

• I agree to contribute to the project under OpenCV (BSD) License.
• To the best of my knowledge, the proposed patch is not based on a code under GPL or other license that is incompatible with OpenCV
• The PR is proposed to proper branch
• There is reference to original bug report and related work
• There is accuracy test, performance test and test data in opencv_extra repository, if applicable
  Patch to opencv_extra has the same branch name.
• The feature is well documented and sample code can be built with the project CMake

[asmorkalov]

@vpisarev could you look at it?

[vpisarev]

@ruelj2, thank you for the contribution! It's much better, but still I can find many many similarities, e.g. in the rect_improve, like variable names, comments etc. That is, the code does not seem to be written from scratch, but rather a refactored original implementation

[jeanchristopheruel]

Thanks for the review! As the original issue with license conflict #2016 stated, the only code that seemed to be conflicting was the "Compare doubles by relative error" which is the only thing I changed from the original code.

As mentioned here, it now seems that the whole code should be refactored from scratch. Working on that, closing the PR.