oda spec fixes

[rurban]

The current ODA spec has too many bugs and omissions.
We reverse-engineered their pdf to a simple markdown document, which can produce equal pdf's, and came to this diff.
https://github.com/LibreDWG/libredwg/blob/master/doc/ODA-5.4.2-libredwg-diff.pdf

I don't think that you are allowed to copy and publish their original pdf.

The various missing objects and entities are described at https://github.com/LibreDWG/libredwg/blob/master/src/dwg.spec

[DJGosnell]

@rurban @DomCR
Thank you for bringing up this topic as I believe this was going to come around sooner or later and it is a very important one since this project has gained traction.

The main thing is licensure. Since this project is currently MIT, are you granting the right for this project to use the LibreDWG spec without switching the license of ACadSharp to GPL3? It is pretty critical to maintain a MIT or similar license as GPL3 code in the C# arena is pretty much a contribution and usage death sentence.

[rurban]

I cannot grant any license, the FSF owns it. But the spec is just docs and a clean-room translations of the ODA spec.
Any additions and fixes from this spec are also just docs, not code.

[DomCR]

Thanks a lot for the resource!