cadnano import should use helices_view_order to preserve the main view ordering of helices as they appear in cadnano #202
Description
See UC-Davis-molecular-computing/scadnano#673.
Import this cadnano design. It appears the helices have incorrect parity:
leading the design to have large spacing between every other pair of helices:
Presumably the original cadnano design had all these helices spaced equally and on top of each other in the square lattice, in order 0, 1, 2, 3, ...