[Changeset]: Add the plotmatrix function

[John W. Eaton]

On 21-Sep-2008, David Bateman wrote:

| Not sure how much use this function really is, but as it and comet are 
| the only 2D core matlab plotting functions that aren't implemented, for 
| completeness I include an implementation of this function here.

I applied the changeset.

Thanks,

jwe