SetMask_SphericalSurface sets a mask based on SphericalSurface information. At every invocation, it wipes the mask, then resets it. Old behavior: mask is set from surface only if surface is active and valid. However, sometimes finding a horizon with AHFinderDirect may fail, but the mask info (i.e. the radius) may be perfectly valid. Mask is still not set in the old behavior, because AHFinderDirect makes the mask invalid (-1) if it does not find a horizon. New behavior: set mask from surface is surface is active and its minimum radius is > 0.
Pull request also adds verbose output (default: off).