Add support for IGES file format

[VikingScientist]

Add a writer for IGES file format. The format is more general than is currently supported in splipy, so priority is to be given to the writer function and then we might consider how to approach the reader option.

[lajfriedrich]

This feature would be great indeed! May I ask what is the development status?
I know this feature is available in MATLAB for the NURBS package http://rafavzqz.github.io/geopdes/download/ see the file nrb2iges.m

[VikingScientist]

There is currently no ongoing activities working on this feature so it is not expected in the near future.

After looking briefly into the specs for this, then it appears that it has not been updated in 25 years. From the wikipedia page on IGES:

After the initial release of STEP (ISO 10303) in 1994, interest in further development of IGES declined, and Version 5.3 (1996) was the last published standard.

and also

An IGES file is composed of 80-character ASCII records, a record length derived from the punched card era

It is not very motivating working to support such ancient technology. I expect that we will first provide support for STEP files (issue #133) or Rhinoscerous 3D files (pull request #135)

[RiekeJ]

IGES is one of the most wide spread data exchange formats for b-spline/NURBS in engineering. Nearly every CAD/FEA/CFD/mesher tool supports it. Compared to STEP it might be far more easy to realize. The "puch card" like format might be annoying, but works great - even if ancient. I've written exporters to IGES for my little playground Fortran NURBS lib some time ago. The cited Matlab code might be a good start. IGES support from Splipy would be highly appreciated.