Dataset collections - backbone model.
More reworking of backbone views to allow multiple content types.
Dataset collections - backbone view.
Dataset collections - workflows - handle data_collection params in editor.
Dataset collections - workflows - handle implicit map/reduce in editor.

Track which inputs are multi-run on each tool - if any are - update all outputs to likewise by multi-run and propage. Fixup can_accept logic for matching data collection inputs and multi-run outputs to inputs. Allow implicit dataset collection reduction steps when connecting a multi-run output or dataset collection input step to a multiple input data parameter.
Dataset collections - workflow editor UI display different connector for implicit map steps.