When PNG has fewer colors than 255+1, consider force saving as palette image

[mosbth]

The following code was removed from load()

        /* Removed v0.7.7
        if (image_type_to_mime_type($this->fileType) == 'image/png') {
            $type = $this->getPngType();
            $hasFewColors = imagecolorstotal($this->image);

            if ($type == self::PNG_RGB_PALETTE || ($hasFewColors > 0 && $hasFewColors <= 256)) {
                if ($this->verbose) {
                    $this->log("Handle this image as a palette image.");
                }
                $this->palette = true;
            }
        }
        */

Consider to move it to save() instead.