automatically set Helix rolls based on crossover locations ("relax" the rolls) #257
Description
Unlike "set helix coordinates based on crossovers", this would not adjust helix positions, only their rolls.
Keep each helix in the same position, but adjust the roll to minimize "something" about the strain. One way to do this is to calculate how far is each crossover from being perfect, e.g., if a crossover goes from helix i to j, but instead of the backbone angle pointing straight at j, it is 20 degrees off, then the "error" is 20 degrees. We could minimize the sum of squared errors for each crossover, for instance. This should be a straightforward linear algebra calculation to compute this roll for each helix.