#351 Add a colored icon to the system tray

[Andre Nogueira]

While doing development many people leave NUnit running on the background, set to automatically reload and rerun the tests whenever the assemblies change.

An always-present visual clue would allow developers to easily and quickly see the status of a given build without having to change to the NUnit GUI app, or ever leaving their development environment.

A good way of implementing this would be to add the option of having NUnit system tray which changes to the appropriate test result color (green, yellow or red) each time the tests are run.