yagp: Force images to a 4x4 grid

This gets rid of the problem with images appearing all over the place.

The size of the grid can be adjusted by changing the IMGS_PER_PAGE and
IMGS_PER_ROW #define's.

Signed-off-by: Andrew Clayton <andrew@digital-domain.net>
css: Set the <td> colour to black

Switching to the grid layout caused the text for the thumbnails to
change to an off white colour due to the css in td.td_index

Put this back to black like it was before.

Signed-off-by: Andrew Clayton <andrew@digital-domain.net>