Implement copy and assignment operators for Vertex2D

Refs #8360
Implement copy and assignment operators for Quadrilateral.

Quadrilateral specialies ConvexPolygon to avoid heap allocations
so the copy and assignment operators need to be aware of this.
Refs #8360
Fix memory leaks in LaszloIntersection code.

This only affected the cases where exceptions were thrown.
Refs #8360