Improvements on original decoITS project to be run with Unity

Minimal changes to support running tutor with Unity project.
Some of the changes included are:

• Removed dependency on System.Configuration for config file use. Now project comes with ITutorConfig and a default implementation (that still relies on System.Configuration) so other projects are free to implement their own configuration strategy.
• Downgraded project to be built against .Net v3.5 to be run with Unity stable runtime.
• Merged bug fixes by UPM GATE team.