Greater control over Node labels

[nowthis]

Come up with an intuitive syntax for these extra features:

• Substituting text for Node labels, as in:
  • within the flow specs, always use a nice short unique name ('xyz')
  • in the Node spec, provide the actual longer name for display use ('Xtra Yellow Zippers')
• Suppress the display of a node's name in the graph
  • e.g. for a budget, we might put the total in the informative Title and not need to label the middle node at all.