image resizing improvement

with this patch images will resize by original file aspect ratio
in imagecache preset screen u need to set one variable for image dimension
if u set height 0 or leave blank then height will set by width auto
if u set width 0 or leave blank then width will set by height auto
code implemented by huzursuz ipnesi

#172 foreach ($actions as $action) {
#173 $size = getimagesize($tmpdestination);
+++ if (($action['data']['height'] == 0) or is_null($action['data']['height'])) {
+++ $action['data']['height'] = round($size[1] * ($action['data']['width'] / $size[0]));
+++ }
+++ if (($action['data']['width'] == 0) or is_null($action['data']['width'])) {
+++ $action['data']['width'] = $size[0] * ($action['data']['height'] / $size[1]);
+++ }