Do not report warning (Missing nodes/models) when switching between opened workflows

[christian-byrne]

Fixes #573 by adding options param to loadGraphData with type:

interface LoadGraphDataOptions {
  showMissingNodesDialog: boolean
  showMissingModelsDialog: boolean
}

Missing nodes/models not reported on (1) switches between open workflows or (2) undo/redo.

[huchenlei]

@christian-byrne I have invited you as collaborator of the project. Please confirm the invite. Thanks!

[christian-byrne]

The extra kwargs probably don't need a separate interface. I can help fix that.

Good to know, and thanks.