Moved cs files into Services/Models folders
Extracted song loading into seperate class.
Files open in BackgroundWorker
As files load: UI updates & buttons are disabled.
Retargeted to .NET 4.0
Hardcoded CallerMemberName for .NET 4.0
Fixed missing notes due to foreach closure bug

http://blogs.msdn.com/b/ericlippert/archive/2009/11/12/closing-over-the-loop-variable-considered-harmful.aspx

Added test project