grade-school: add canonical data
grade-school: add canonical data

closes #561
This testdata is based on implementations of this exercise in the csharp and Delphi tracks.
jmluy/x-common,rpottsoh/x-common,exercism/x-common,rpottsoh/x-common,jmluy/x-common,petertseng/x-common,jmluy/x-common,ErikSchierboom/x-common,exercism/x-common,ErikSchierboom/x-common,petertseng/x-common