Semantic environment API

[adamdbrw]

I would like to be able to query the simulation for meaningful points in two contexts:

1. As points for navigation, for example, where to go for Palletizing, Wrapping, CargoStorageDrop, CargoPickup, CargoDelivery, Charging, etc. The call needs to have enough arguments for deterministic answer (e.g. what robot am I?).
   The response should be at least a Pose (for directed approach) that should be a valid navigation goal.
2. An API to return points of interests (which can be added to the scene as entities/prefabs or tags). This is to direct a randomized "inspection" behavior.