Add "openhorizon.node.id" to the set of built-in properties on nodes.

[TheMosquito]

When a node is registered with ID, say "myorg/myid" then add this as a built-in property to the node policy (along with the other built-ins, like openhorizon.memory, etc.). This will enable customers to target or exclude individual nodes in policy constraints, e.g., "openhorizon.node.id != "foo" AND ...". This would be useful in many real world scenarios for customers. Of course normally they will target groups of nodes, but they will also sometimes want to target or exclude individual nodes.