Provide type conversion: PackageVersion to System.Version

[jaigak]

WinRT APIs related to packaging return a PackageVersion structure for reporting version info which can't be directly passed to code that expects System.Version, so consider adding an implicit conversion on PackageVersion to the System.Version class.

[Marv51]

I would like this very much! From my past experience the quick note, that the version structs differ in data type: System.Version uses int32 and PackageVersion ushort. But for the direction you are suggesting, that shouldn't be an issue.