If possible use Toast notify instead of Tray notify

[sboulema]

• On Windows 8 and higher use Toast notifications: https://msdn.microsoft.com/en-us/library/windows/apps/hh465391.aspx instead of Tray notifications that are more easily missed
• Right now the two options for notifying about tests are dependent on each other. Remove the dependency and simplify the logic for notifying.
  Beep when a test run is completed -> notify always regarding of outcome
  Beep when a test run is completed and there are failed tests -> notify only when there are failed tests