Desc format

[fbeutel]

Suggestion for a new format for the desc output dictionary.
This follows more closely the idea of GDSII that each cell is identified by a unique name and can be referenced mulitple times.

With this new format, the resulting dict will only contain the desc data for each cell once and just store (name) references to the other cells.

Basically, the resulting dict will look somewhat like this:

{
    "root": "name_of_root_cell",
    "cells": {
        "name_of_root_cell": {
            "desc": {...},
            "cells": [ <list of all cells referenced by this cell (with origin, angle etc.)>  ]
        },
        "other_cell": {
            "desc": {...},
            "cells": [ <list of all cells referenced by this cell (with origin, angle etc.)>  ]
        },
    }
}