A Types/NoiseExpression together with a name.
Named noise expressions are used to specify functions for elevation, temperature, moisture, aux, and cliffiness.
In 0.16 the 'name' of the NamedNoiseExpression must be "default-<property>", e.g. "default-elevation" for it to be picked up by the terrain generation system and used to calculate elevation.
Inherits all properties from Prototype.
The expression itself.