Add multiple scales to the graph #4
Description
This is not MTGs (necessarily) but basically emulating graph_data() to access different scales. This means that a node can belong to different scales and that we can have different groups at each scale (the simplest example would be the branch scale).
Geometry generation should be defined per scale so that we can create different degrees of detail in geometry (e.g., a branch could be turned into a single geometry object, rather than every organ within the branch). A possible design is to have multiple graphs stored together and special links to move from graph to the other.
Another possibility is to define intrascale and interscale edges. So a node can have one parent within a scale and another parent in an other scale. Similarly, children will exist within and across scales. Every graph traversal method could then be repeated to jumping across scales. A turtle would only traverse within a scale.
The remaining issue is how to modify the graph construction DSL as we need to add a new type edge (interclass analogies for + and ()).