simplify extractor constants

- single strings for URL patterns
- tuples instead of lists for 'directory_fmt' and 'test'
- single-tuple tests where applicable

gallery_dl/extractor/recursive.py

@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 
-# Copyright 2015-2018 Mike Fährmann
+# Copyright 2015-2019 Mike Fährmann
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 2 as
@@ -17,10 +17,10 @@ import re
 class RecursiveExtractor(Extractor):
     """Extractor that fetches URLs from a remote or local source"""
     category = "recursive"
-    pattern = [r"r(?:ecursive)?:(.+)"]
-    test = [("recursive:https://pastebin.com/raw/FLwrCYsT", {
+    pattern = r"r(?:ecursive)?:(.+)"
+    test = ("recursive:https://pastebin.com/raw/FLwrCYsT", {
         "url": "eee86d65c346361b818e8f4b2b307d9429f136a2",
-    })]
+    })
 
     def __init__(self, match):
         Extractor.__init__(self)