Change test file from GradeSpec to Rank Spec
Move persistence files to a new package for visibility
Merge branch 'usecase-grade'
Edit getRanks, getSpecificRank and newRank with the new link to Corps
Now handling corps creation when label given with new rank
Delete the unit test files that weren't running properly
Finishing this usecase. Now a Rank has a Corps and can be modified/deleted.
Fix typo on comment
Fix update
Forgot one verif on update rank