rename media plugin to ytdlp with backwards-compatible aliases

- Rename archivebox/plugins/media/ → archivebox/plugins/ytdlp/
- Rename hook script on_Snapshot__63_media.bg.py → on_Snapshot__63_ytdlp.bg.py
- Update config.json: YTDLP_* as primary keys, MEDIA_* as x-aliases
- Update templates CSS classes: media-* → ytdlp-*
- Fix gallerydl bug: remove incorrect dependency on media plugin output
- Update all codebase references to use YTDLP_* and SAVE_YTDLP
- Add backwards compatibility test for MEDIA_ENABLED alias

etc/ArchiveBox.conf.default

@@ -11,7 +11,7 @@
 # RESTRICT_FILE_NAMES = windows
 # ONLY_NEW = False
 # TIMEOUT = 60
-# MEDIA_TIMEOUT = 3600
+# YTDLP_TIMEOUT = 3600
 # URL_BLACKLIST = (://(.*\.)?facebook\.com)|(://(.*\.)?ebay\.com)|(.*\.exe$)
 # CHECK_SSL_VALIDITY = True
 # RESOLUTION = 1440,900
@@ -36,7 +36,7 @@
 # SAVE_SCREENSHOT = True
 # SAVE_DOM = True
 # SAVE_GIT = True
-# SAVE_MEDIA = False
+# SAVE_YTDLP = False
 # SAVE_ARCHIVE_DOT_ORG = True