Structural age calculates incorrectly for topology networks

[samthiele]

Structural age of edges in the NoddyTopology class calculates incorrectly for unconformities, with stratigraphic units deposited after the unconformity assigned their stratigraphic age rather than the age of the unconformable package.

The problem is best illustrated by creating a model with a initial stratigraphy, fold, unconformity and fault and then plotting a hive diagram. Units deposited after the unconformity are assigned a structural age that is much too high ( younger event than the fault), rather than the age of the unconformity. I am unsure how to best fix this.