SAK-26583 Added GradebookInformation class to the API.The class is kind of duplicate of GradebookDefinition class. Adding Assignment information in category

git-svn-id: https://source.sakaiproject.org/svn/edu-services/branches/SAK-26583@311026 66ffb92e-73f9-0310-93c1-f5514f145a0a