Migrate to System.CommandLine

[petrsvihlik]

Microsoft.Extensions.CommandLineUtils is no longer being maintained by MS and was forked to: https://github.com/natemcmaster/CommandLineUtils

From the long-term perspective, it might make sense to migrate to a standard .net command-line parser:

https://github.com/dotnet/corefxlab/tree/master/src/System.CommandLine

Could help solve #45

[brunotag]

Hey keen to pick this up, just one thing: System.CommandLine is currently in pre-release, are you sure you wanna use it?

https://dotnet.myget.org/feed/dotnet-corefxlab/package/nuget/System.CommandLine

[petrsvihlik]

Hi @brunotag No, I haven't noticed that. Do we know when it's gonna be RTMed?

[JanLenoch]

Fixed by #56