Dataset collections - create lists and pairs via HDA multi-select.
Dataset collections - backbone model for history content.
More reworking of backbone views to allow multiple content types.
Dataset collections - backbone view for history content.
Add helper destroyInvalidConnections to Terminal.

Used in current workflow and reused in different context in collection code.
Mechanism for connecting far away nodes.
Dataset collections - update workflow editor for collection inputs, mapping, and reduction.

This commit enables the workflow editor to deal with input collection data parameter types and inputs (easy) and much more complicatedly reason about mappings and reductions over inputs and collection inputs. Not sure I can really describe the new interface in a changeset - essentially it is more complicated to determine if a input can be connected to by an output - and that connection affects what are valid other inputs and what the outputs are.