React prototype

This is a branch that creates a view with React components. The App component contains an AST editor and a Graph component. A Graph component receives a dummy model (a simple wrapper around an AST) and renders a set of Node components. A Node component is a rectangle of a constant size and a given position. Dragging a Node element changes the node's position in the model. That change causes the view to re-render from the App component down.
That is correct. The AST and Symbol Table are both intermediaries to the data model; no one (except the language team) should be directly coding against either the AST or the Symbol Table implementations once they are in place.

I might start cleaning up the dataModel branch and merging in what we have since it's becoming a major bottleneck. Expect a PR if I can get my AST stuff done today.