Allow using vertices when constructing lofts

[adam-urbanczyk]

trafficstars

E.g.

import OCP

bldr = OCP.BRepOffsetAPI.BRepOffsetAPI_ThruSections(True, False)

w1 = cq.Workplane().ellipse(5,10).val()
w2 = cq.Workplane(origin=(0,0,10)).ellipse(12,25).val()
v1 = cq.Vertex.makeVertex(0,0,15.5)

bldr.AddWire(w1.wrapped)
bldr.AddWire(w2.wrapped)
bldr.AddVertex(v1.wrapped)

res = bldr.Shape()

s = cq.Workplane(obj=cq.Shape.cast(res)).faces('<Z').shell(-1,'intersection')
show_object(s)

[adam-urbanczyk]

Need to check how ESP does it: