Extend analyzers

[Corniel]

To further improve the code base the following analyzers have been enabled:

• DotNetProjectFile.Analyzers
  Checks the settings of MS Build project files. All suggestions have been applied.

• IDisposableAnalyzers
  Rules to ensure that the IDisposable pattern is applied correctly.

• SonarAnalyzer.CSharp
  370+ rules on writing better code.

• Enabled nullability checks
  To help preventing null dereference exceptions.

I moved the configuration about the analyzers from the .editorconfig to the .globalconfig file.

[phmonte]

@Corniel I'm ready to merge, If you can resolve the conflicts, if you can't, I can resolve them, just let me know, Thanks.

[Corniel]

Rebase applied.

[phmonte]

@Corniel ,
Thanks, it took me a while because I was reading about DotNetProjectFile.Analyzers and IDisposableAnalyzers