Switch "rows" and "columns" in shape-check for Z matrix in addcoords.

The first index of a matrix is (generally) the row or number of rows,
and the second the number of columns. Change the check (or, if you
rather, the error message) to conform with this convention.
Add support for list of coordinates to surf.

Change surf so that it can take a one-dimensional matrix Z as its third
argument. Understand the element Z[i] to be the z-coordinate corresponding to
(x[i], y[i]). (Consider, for example, surf(1:10, 1:10, 2*[1:10].^2, "plotstyle,
"points"). )