Bug 602761 - plug-in-grid: Parameters Horizontal/Vertical Spacing and Horizontal/Vertical Offset are reversed

Revert commits bc099a98 and
c77781de from Jul 27 2006;
also changed refval boundaries of the "width" size entries
in the spirit of the original fix, only reversed.

Rationale: the "horizontal" parameters all have to affect the
horizontal *lines*, so have an effect in *vertical* direction.

Will commit a label change on top to clarify this.