Dynamic tables

[Keavon]

Appends data that gets sent along in the node graph data flow. For example, appends a "color" attribute to each point in a list of points, allowing shapes instanced at those points to be colored accordingly. Or it can append the data for a color palette at the root of a document and that gets sent along to all descendants in the graph which can access that palette information.

See design details at #2522.