.NET Core 3.0 support

[mauroservienti]

• [x] Move Radical to .NET Standard https://github.com/RadicalFx/Radical/issues/258
• [x] Move Radical.Windows to .NET Core 3.x https://github.com/RadicalFx/Radical.Windows/pull/93
  • [x] Currently blocked by https://github.com/Microsoft/XamlBehaviorsWpf/pull/20 has been merged to master, scheduled to be released beginning of November. Released to nuget.
• [x] Evaluate merging Radical.Windows and Radical.Windows.Presentation into a single Radical.Windows package.
• Move Radical.Windows.Presentation to .NET Core 3.x merged into Radical.Windows
• Evaluate options for DI. e.g. Move away from dedicated packages for DI containers https://github.com/RadicalFx/Radical.Windows.Presentation/pull/23. Or completely move away from DI into a pure DI direction. everything moved to IServiceCollection
  • Rework IoC related packages

[mauroservienti]

.NET Core 3 support is now in beta. Closing this. Ongoing work is tracked by https://github.com/RadicalFx/Radical.Windows/milestone/3, https://github.com/RadicalFx/Radical/milestone/7, and https://github.com/RadicalFx/documentation/milestone/1