This class implements an I3S layer. In CesiumJS each I3SLayer creates a Cesium3DTileset.
Do not construct this directly, instead access layers through I3SDataProvider.
Members
    Gets the I3S data for this object.
    When 
true, when the loaded I3S version is 1.6 or older
    The major version number of the loaded I3S dataset
    The minor version number of the loaded I3S dataset
readonly resource : Resource
    Gets the resource for the layer.
readonly rootNode : I3SNode
    Gets the root node of this layer.
readonly tileset : Cesium3DTileset
    Gets the Cesium3DTileset for this layer.
    The version string of the loaded I3S dataset
