primitive Swing UI for exploring trees
- and a phase to capture them; try adding `>>> DebugPhase`
flatten group not followed by a project (Fixes #422)
- and fixed the schema in groupBy
- and moved the RenderTree[Grouped] instance to the correct companion obj.
don't project under "value" if shape is known (Fixes #398)

- with an integration test
- and mark a related test as no longer pending
Merge pull request #424 from mossprescott/ready/398

don't project under "value" if shape is known (Fixes #398)
Merge pull request #419 from mossprescott/ready/tree-viewer

primitive Swing UI for exploring trees
Tighten up WorkflowBuilder types.

Mostly: don’t use a disjunction where we don’t need it.
Merge pull request #425 from sellout/ready/minor-fixes

Tighten up WorkflowBuilder types.
integration test for wildcard with groupBy
Merge remote-tracking branch 'upstream/master' into ready/422
Merge pull request #423 from mossprescott/ready/422

flatten group not followed by a project (Fixes #422)