v.0.8.0

breaking change: renamed some config options (see below). if you use them, you need to update your custom/config.php or gallery.txt files. you can also delete all files inside cache/zip/, because all zip files will be re-created with this update

• renamed the config option default_image_quality to image_quality_jpg and default_modern_image_quality to image_quality_webp and image_quality_avif
• renamed config options download_image_enabled to download_image and download_gallery_enabled to download_gallery
• 'end session' link to lock secret galleries
• zipped gallery downloads now use the download_filetype option (set to false to download the original files)
• gallery downloads now also check the image filesize to determine if an image changed and a new cache file needs to be created
• small design enhancements