new feature: draw BOUNDBOX BEST
-- draws the best box around currently selected atoms
bug fix: a.distance.min(b).min should not report 0 if a == b. (testing atom against itself should be skipped)
bug fix: SHOW BEST ROTATION just shows the current rotation, not the best rotation to use to get to the best view
bug fix: rotate BEST can fail with flat structures
bug fix: LOAD "" FILE BOUNDBOX does not include all atoms