[BUG] using unconformities doubles time to evaluate model

[lachlangrose]

Describe the bug
If unconformities are added into the model the time taken to evaluate the model increases by about double. Map2loop example 130 seconds without unconformities 260 seconds with unconformities. Its only really an issue when dealing with big models.

This is because the unconformity is a copy of the stratigraphy and so we have to evaluate the whole fault network before being able to evaluate the location of the unconformity.

No obvious workarounds.

Need to integrate the unconformity into the scalar field of the stratigraphy.