Function setThemeColumns
controls the thumbnail layout of themes.
Uses the theme options: albums_per_row albums_per_page images_per_row images_per_page
Computes a normalized images/albums per page and computes the number of images that will fit on the "transitional" page between album thumbs and image thumbs. This function is "internal" and is called from the root index.php script before the theme script is loaded.