Corr Manipulation Constraints

Two variables can be manipulated, either vertically (arcs on top and
bottom of variable circle) or horizontally (arcs on left and right of
variable circle). The control follows pointer movement on the plot
window.

Vert: Vertical manip variable manipulation is constrained along a
vertical latitude line.

Horiz: Horizontal manip variable manipulation is constrained along a
horizontal longtitude line.

Combined: Both variable can be manipulated by mouse movement.

Equal Comb: Both variables can be manipulated but the amount is the
same horizontally and vertically.

USAGE WARNING: There is one case where the controls for the manual
correlation tour is unresolved:
  When the horizontal manip variable is active in the vertical direction
  or the vertical manip variable is active in the horizontal direction.