Fix to allow multistructure images in Java/C# and use MCS for c# wrapper

[jones-gareth]

What does this implement/fix? Explain your changes.

This pull request does two things-

1. Simple change to the MolDraw.i swig interface so that I can create a ROMol_Ptr_Vect in Java or C# and draw those molecules using MolDraw2DSVG

2. A change the the csharp_wrapper CMakeLists.txt to use mcs as the mono compiler rather than gmcs (which isn't shipped any more). Without this change it is not possible to create a makefile for building the wrapper.

Any other comments?

The current code base does not compile the c sharp assembly as PropertyPickleOptions.cs will not compile. As I don't need that code I can delete that file and compile manually.

I'm using dotnet core to build a Linux library. If it's of interest and I could look at replacing mcs with dotnet in CMakeLists.txt.

I've published a Nuget package for dotnet core on Ubuntu built on Rdkit 2019.9 release. We're using it to run dotnet services on Linux containers.

[greglandrum]

Thanks @jones-gareth : this is an easy one to review and approve. :-)

Thanks too for doing the nuget package. Maybe you, @bp-kelley, and I can talk about figuring out how to make building the linux and windows nuget packages easy enough (or automated) so that we can regularly update them when new RDKit releases are done.

[bp-kelley]

FYI: My preferred way of building the c# wrappers and NuGet is here:

https://github.com/bp-kelley/rdkit-csharp

The only build dependencies are swig and cmake.

I haven’t made a Linux build, but I’ll try the windows build with this fix. I don’t remember it being an issue on windows though.

[jones-gareth]

@greglandrum Would be happy to help with managing nuget packages

@bp-kelley Thanks for the pointer to the script. I'd like to have a way to support dotnet core for both windows and Linux in the same nuget package- given you build for both 32 and 64 bit I'm hoping this will help

[bp-kelley]

@jones-gareth I think all we would have to do is modify the nuget info, and put all the artifacts together:

https://github.com/bp-kelley/rdkit-csharp/blob/master/RDKit2DotNet.csprog.nuspec