Update to able run with Blazor version 0.6.0

[sergeysolin]

• Upgraded nuget packages:
  • Microsoft.AspNetCore.Blazor.Browser => 0.6.0
  • Microsoft.AspNetCore.Blazor.Build => 0.6.0
  • Microsoft.AspNetCore.Blazor.Server => 0.6.0
  • Microsoft.AspNetCore.Razor.Design => 2.1.2
• Converted Client project to use new startup template (using Startup.cs file)
• Removed ILayoutComponent dependencies, replaced with BlazorLayoutComponent
• Updated js code running logic to use Microsoft.JSInterop
• Replaced legacy JsonUtil with Json from Microsoft.JSInterop

[torhovland]

Thanks for this, Sergey!