[winforms-dotnet5] Move content - Dialogs and popups

[adegeo]

Related to #72

When porting and migrating source content (presented as a link that goes to an article), open the source material up. Find out where it exists in the TOC. In the source project #72 navigate down to the .NET Framework 4 TOC and my notes collapsible region and expand it. Find the article title in the TOC and review the notes.

• Dialogs and popups
  This content should mirror what is in WPF. This content doesn't really exist in the .NET Framework winforms area
  • Overview (link link (WPF))
  • Common tasks
    • Display a message box (link (WPF))
    • Open a form (link (WPF))
    • Close a form (link (WPF))
    • Display a system dialog box (link (WPF) link)
    • Get or set the main form (link (WPF))