Update samples for easy execution

[daveMueller]

I've seen that the examples in Documentation\Examples need code changes before they can be executed. Mainly this is caused by the roslyn-analyzers that changed with editing our EditorConfig file. Here is an example:

PS D:\Repos\coverlet\Documentation\Examples\VSTest\HelloWorld> dotnet test --collect:"XPlat Code Coverage" --settings runsettings.xml
  Determining projects to restore...
  Restored D:\Repos\coverlet\Documentation\Examples\VSTest\HelloWorld\XUnitTestProject1\XUnitTestProject1.csproj (in 34
  8 ms).
  1 of 2 projects are up-to-date for restore.
D:\Repos\coverlet\Documentation\Examples\VSTest\HelloWorld\ClassLibrary1\Class1.cs(1,1): error IDE0073: A source file i
s missing a required header. [D:\Repos\coverlet\Documentation\Examples\VSTest\HelloWorld\ClassLibrary1\ClassLibrary1.cs
proj]
D:\Repos\coverlet\Documentation\Examples\VSTest\HelloWorld\ClassLibrary1\Class1.cs(1,1): error IDE0005: Using directive
 is unnecessary. [D:\Repos\coverlet\Documentation\Examples\VSTest\HelloWorld\ClassLibrary1\ClassLibrary1.csproj]

[Bertk]

Please consider another topic as well. Some old source code files are not complaint to current .editorconfig settings.

• source file encoding (UTF-8)
• Whitespace settings
• …

This can be resolved with dotnet format for all source code files and will improve the PR review activity.