DB: add Dataset
DB: add SubmissionResult
DB: add UserTestResult
grading: Job
grading: get_task_type
grading: get_score_type
grading: update to use SubmissionResults
services: update get_submissions to get_submission_results
services: add function to get all to-autojudge datasets for a task
ES: loads of changes
SS: loads of changes
SS: fixup
SS: fixup
CWS: loads of changes
AWS: add handlers for Datasets
AWS: fix Manager and Testcase handlers
AWS: update to use SubmissionResults
AWS: allow to see submissions on a certain dataset
AWS: fix (3)
AWS: fix (6)