Accessibility problems with display and editing of Matrix

On all branches of this module the row title is not apporpriately tagged as a header and should also contain a scope attribute so that matrix results can be more legible to screen-readers. Also, when editing a matrix the #title of fields is not set, making the label not display for screen readers.

Attached is a patch to add a header to the first title cell of rows and labels that concatenate the column and row title into a label.