Add _repr_svg_()

[Stoops-ML]

An SVG image is displayed for BaseCZMLObject() objects that have Position() or PositionList() attributes (if defined). The Colour() attribute is used if defined, else black is used.

No image is displayed for BaseCZMLObject() objects that don't have Position() or PositionList() attributes, nor for BaseCZMLObject() objects that don't have Position() or PositionList() attributes defined.

This is supported for:

• Polyline()
• Polygon()
• Position()
• PositionList()
• Packet()
• Wall()
• Corridor()

Note that the Packet() class combines all SVGs that it contains, and supports Point() and Path() classes which have their positions defined externally (i.e. within the packet and not within themselves).

An example in Jupyter lab:

p = Packet(
        id="AreaTarget/Pennsylvania",
        name="Pennsylvania",
        position=Position(
            cartographicDegrees=[38, 38, 10]
        ),
        point=Point(
            show=True,
            pixelSize=10,
            scaleByDistance=NearFarScalar(
                nearFarScalar=NearFarScalarValue(values=[150, 2.0, 15000000, 0.5])
            ),
            disableDepthTestDistance=1.2,
            color=Color(rgba=[200, 100, 30, 255]),
        ),
        polygon=Polygon(
positions=PositionList(
    cartographicDegrees=CartographicDegreesListValue(values=[37.2, 37.3, 10, 38, 38, 10, 37.5, 36.9, 10])
),
material=Material(solidColor=SolidColorMaterial.from_list([200, 100, 30])),
),
polyline=Polyline(
    material=Material(solidColor=SolidColorMaterial.from_list([0, 255, 0])),
    positions=PositionList(
        cartographicDegrees=CartographicDegreesListValue(values=[37, 37, 10, 36, 36, 10])
    ),
    arcType=ArcType(arcType="GEODESIC"),
    distanceDisplayCondition=DistanceDisplayCondition(
        distanceDisplayCondition=DistanceDisplayConditionValue(values=[14, 81])
    ),
    classificationType=ClassificationType(
        classificationType=ClassificationTypes.CESIUM_3D_TILE
    ),
)
    )
p

[Stoops-ML]

Forgot to run flake8. I'll close this and do another PR.