Upgrade to .net 4.7.2 and .net core 3 (WIP)

[Gitii]

Hi,

I converted all projects to sdk style.
NodeNetwork & -Toolkit are now targeting .net 4.7.2 and .net core 3.

I haven't touched the code or dependencies, except:

• upgraded System.Reactive & related packages to 4.2.0
• project files and package files
• ExampleShaderEditorApp uses .net 4.7.2
• ExampleCodeGenApp & ExampleCalculatorApp use .net core 3.0

It is not ready to be deployed because there are several (light) issues:

• (critical) ExampleShaderEditorApp does not build: There seems to be some dependency issue with OpenGL.net
• Several warnings about not .net core compatible dependencies. Most of them are either false positives or the incompatible code is not used.

All Unit tests are passed, both ExampleCodeGenApp & ExampleCalculatorApp are working without issues.

I think it's a good start. Depending the use case, it might even be ready to use.

Greetings,

Gitii

[Wouterdek]

Hi,

Thanks for your contribution! Last time I checked there were quite some issues with .net core so it's good to see that most of those seem to be resolved. A previous PR (#26) also mentioned problems with the opengl package. The issue might be solvable by using a different package or switching to directx, for which there is probably native support.

I'll look into this more at the end of this month.

[Gitii]

Hi,

the biggest issue is OpenGL.Net which seems to have major issues with Net Core 3: luca-piccioni/OpenGL.Net#147. Removing some props of the GL control let the build complete but the control is all black (no exceptions). I have no experience with OpenGL, maybe a different wrapper/binding is a valid solution.
There are other dependencies of NodeNetwork which are not available for Core 3 but can be used anyway (unit tests and 2/3 example apps are working...).
I recommend that you release a beta version and test the water.
There may be newer versions of some dependencies which already support Net Core 3.
I haven't touched those because I wanted to avoid any unwanted side effects (in other words bugs or api changes) when upgrading.

Greetings,

Gitii

[Wouterdek]

I replaced OpenGL.net with opentk, which seems to work fine. I also made a few other tweaks, but nothing major.
I've merged the PR, and the next release will have .net core 3.1 support.

Thanks for the PR!