Replace autogenerated names for anonymous subschemas with an :anonymous atom

[dragonwasrobot]

Rather than naming the subschema at allOf/0 below `Zero, or similar autogenerated names,

"allOf": [
        {
            "type": "object",
            "properties": {
                "color": {
                    "$ref": "#/definitions/color"
                },
                "description": {
                    "type": "string"
                }
            },
            "required": [ "color" ]
        },
        {
            "$ref": "#/definitions/circle"
        }
    ],

instead give it an explicit :anonymous name that can easily be cased upon in a consuming project.

[dragonwasrobot]

Implemented as part of 0505eba