Added FileObject class
Decorators are now part of the Widget class. They can be set as front decorator, or rear.
Added Find method to WidgetContainer to find children from an xPath argument.
Renamed Screen to ScreenWidget
Renamed Screen to ScreenWidget
Added Area object to avoid calls to Unity API's Rect, added tests for Find()
Removed all dependencies to Unity API in Widget and put them in UnityWidget that derives from Widget
Reorganized solution