doc: Improve documentation for 2-D plot functions * doc/interpreter/plot.txi: Rewrite documentation around get/set. * libinterp/interpfcn/graphics.cc(Fget, Fset): Add seealso links. Add additional calling forms for get(). * scripts/plot/bar.m, scripts/plot/barh.m, scripts/plot/comet.m, scripts/plot/comet3.m, scripts/plot/contour.m, scripts/plot/contour3.m, scripts/plot/contourc.m, scripts/plot/contourf.m, scripts/plot/errorbar.m, scripts/plot/gca.m, scripts/plot/gcf.m, scripts/plot/gco.m, scripts/plot/ishghandle.m, scripts/plot/loglogerr.m, scripts/plot/pareto.m, scripts/plot/pcolor.m, scripts/plot/pie.m, scripts/plot/pie3.m, scripts/plot/plotmatrix.m, scripts/plot/plotyy.m, scripts/plot/polar.m, scripts/plot/quiver.m, scripts/plot/quiver3.m, scripts/plot/rose.m, scripts/plot/scatter.m, scripts/plot/semilogxerr.m, scripts/plot/semilogyerr.m, scripts/plot/sombrero.m, scripts/plot/stairs.m, scripts/plot/stem.m, scripts/plot/stem3.m: Improve docstrings.

--- a/scripts/plot/stem3.m
+++ b/scripts/plot/stem3.m
@@ -17,7 +17,9 @@
 ## <http://www.gnu.org/licenses/>.
 
 ## -*- texinfo -*-
-## @deftypefn {Function File} {@var{h} =} stem3 (@var{x}, @var{y}, @var{z}, @var{linespec})
+## @deftypefn  {Function File} {} stem3 (@var{x}, @var{y}, @var{z})
+## @deftypefnx {Function File} {} stem3 (@var{x}, @var{y}, @var{z}, @var{linespec})
+## @deftypefnx {Function File} {@var{h} =} stem3 (@dots{})
 ## Plot a three-dimensional stem graph and return the handles of the line
 ## and marker objects used to draw the stems as "stem series" object.
 ## The default color is @code{"r"} (red).  The default line style is
@@ -35,7 +37,7 @@
 ## @noindent
 ## plots 31 stems with heights from 0 to 6 lying on a circle.  Color
 ## definitions with RGB-triples are not valid!
-## @seealso{bar, barh, stem, plot}
+## @seealso{stem, bar, barh, plot}
 ## @end deftypefn
 
 function h = stem3 (varargin)