task versioning: update DB schema.
task versioning: add AdminWebServer support for managing datasets.
AWS: Fix updating testcases.
Ensure dataset description is unique.
AWS: Bugfix in format string for redirect.
Fix unique constraint for dataset descriptions.
task versioning: create SubmissionResult class/table for per-dataset results.
Don't allow active dataset to be deleted.
Convert task.datasets to dictionary instead of list.
AWS: Check uniqueness of description and error gracefully.
AWS: Fix automatic data set activation bug.

The dataset_version is not known until commit, so we can't use it until then.
AWS: Fix for new datasets collection type.
AWS: Log some generic exceptions to aid debugging.
Minor database fixups.
Add helper function to lookup, and if necessary, create SubmissionResult.
Make Evaluation be dataset-specific.
A mass of changes to use SubmissionResults where required.
Fix uniqueness constraint on evaluations.
ES: Make idle loop aware of dataset versions.
Typo fix in comments.