Lessions learned from the current navigation graph:

• The landmark name should be the unique identifier of a node.
• Edges should be linked to nodes via MemoryIDs
• The nodes need more attributes
  • Entry and exit node to couple free and graph-based navigation

Gui widget:

• Add a navigation graph gui widget similar to the one that we already have (likely copy it)
  • no debug drawer
  • directed edges should be drawn by arrows
  • provide some mechanism to add a new node at the robot's current pose