- updated expressiong to graph() from context().getGraph() in EditorCanvas
- updated LinkController to reset the link to the default color on appropriate behavior.
- In EditorCanvas, addNode with getID() instead of String.valueOf(getIssue())
- In LinkController, check for connection requests to parent node, reject request if so.
- In LinkController, check for connection requests to parent node, change currentColor to DEFAULT_COLOR if so.