Bugfix: Copying datasets to existing and new history at same time.
Previously would give error about set not having an append method.
Allow 'Copy Datasets' page to copy collections as well.
PEP-8 fixes for DatasetInterface.copy_datasets.
Order history.{active,visible}_dataset_collections by hid instead of id.
Change paired collections terminology from left/right to forward/reverse.
If you have paired datasets in your database they will no longer work - send me an e-mail and I can give you an SQL update statement.