doc: Use 'axes' rather than 'axis' appropriately in docstrings. * voronoi.m, axis.m, box.m, caxis.m, datetick.m, grid.m, legend.m, lighting.m, shading.m, title.m, view.m, xlabel.m, xlim.m, ylabel.m, ylim.m, zlabel.m, zlim.m, area.m, bar.m, barh.m, colorbar.m, comet.m, comet3.m, compass.m, contour.m, contour3.m, contourf.m, cylinder.m, ellipsoid.m, errorbar.m, ezcontour.m, ezcontourf.m, ezmesh.m, ezmeshc.m, ezplot.m, ezplot3.m, ezpolar.m, ezsurf.m, ezsurfc.m, feather.m, fill.m, fplot.m, hist.m, line.m, loglog.m, loglogerr.m, mesh.m, meshc.m, meshz.m, pareto.m, patch.m, pcolor.m, pie.m, pie3.m, plot.m, plot3.m, plotmatrix.m, plotyy.m, polar.m, quiver.m, quiver3.m, rectangle.m, ribbon.m, rose.m, scatter.m, scatter3.m, semilogx.m, semilogxerr.m, semilogy.m, semilogyerr.m, slice.m, sphere.m, stairs.m, stem.m, stem3.m, surf.m, surface.m, surfc.m, surfl.m, surfnorm.m, waterfall.m, axes.m, cla.m, gca.m, hold.m, newplot.m, subplot.m: Use 'axes' rather than 'axis' appropriately in docstrings.

--- a/scripts/plot/appearance/axis.m	Sun Jun 25 18:50:44 2017 +0200
+++ b/scripts/plot/appearance/axis.m	Tue Dec 19 12:39:25 2017 -0800
@@ -34,7 +34,7 @@
 ## and sixth specify the limits for the z-axis, and the seventh and eighth
 ## specify the limits for the color axis.  The special values -Inf and Inf may
 ## be used to indicate that the limit should be automatically computed based
-## on the data in the axis.
+## on the data in the axes.
 ##
 ## Without any arguments, @code{axis} turns autoscaling on.
 ##
@@ -92,7 +92,7 @@
 ## Turn tick labels off for all axes.
 ## @end table
 ##
-## Note: If there are no tick marks for an axis then there can be no labels.
+## Note: If there are no tick marks for an axes then there can be no labels.
 ##
 ## @noindent
 ## The following options affect the direction of increasing values on the axes.