Generate fiberTraces from odd/even flats

In order to determine the profile for each isolated fiber, flats will be prepared such that pairs of quartz lamp exposures are prepared, in which for one of the pairs even-numbered fibers are illuminated, and for the other odd-numbered fibers are illuminated.

These odd/even pairs should be merged by the pipeline such to generate fiberTrace s which capture the profile of each isolated fiber.

This requires an update to the ConstructFiberTraceTask or a new, separate task. In either case the updated code would need to take as input visit numbers identifying the even- and odd- exposures.