Dotnet6 support

[nimrof]

Hi all,
This finally adds compilation and support for building for .net 6 in addition to .net 4.8.1
It still needs msbuild to build the gui application, but the rest should be able to compile and run on pure multiplattform dotnet

On github it will do a matrix build to and test combination of release/debug & .net4.8.1/6.

[trojanobelix]

Hi @nimrof, I'm a bit unsure about the status of this PR. Do I need to do anything? The conflicts in the project files are obviously and easy to resolve.

[nimrof]

Hi @nimrof, I'm a bit unsure about the status of this PR. Do I need to do anything? The conflicts in the project files are obviously and easy to resolve.

Hi @trojanobelix ,
I should have announced it much better,
but i wanted someone to check & approve it. it is a "big" change

It should not affect the 4.8.1 version in any way and we can mark the .net 6 as beta so i do not see it as a problem, but sometimes i mess up and its nice to have someone else to check my work.

Will try to merge it when i get off work later today, then i will also close #77

edit: thanks for the check btw 👍

[trojanobelix]

For me, it makes the most sense to use this version in my daily work. Certainly not 100% coverage, but if there are
major bugs we can always go back.

With the new release system, we can also get experience from others more quickly. I would welcome a 6.0 beta