Added support for titles in tauko_boxes

boxes.php: Removed tauko_boxes(), updated tauko_box() to support titles.

style_screen.css: Added support for tauko_box title styling.

boxes-priority: Reverted to previous commit.
                Changed to use tauko_box() and titles.

boxes-gallery: Got rid of tauko_boxes().
               Changed to use tauko_box() and titles.

page-templates/gallery_grid: Enabled tauko_box() titles by default.