decouple extractor initialization

Introduce an 'initialize()' function that does the actual init
(session, cookies, config options) and can called separately from
the constructor __init__().

This allows, for example, to adjust config access inside a Job
before most of it already happened when calling 'extractor.find()'.

gallery_dl/extractor/lolisafe.py

@@ -46,9 +46,10 @@ class LolisafeAlbumExtractor(LolisafeExtractor):
         LolisafeExtractor.__init__(self, match)
         self.album_id = match.group(match.lastindex)
 
+    def _init(self):
         domain = self.config("domain")
         if domain == "auto":
-            self.root = text.root_from_url(match.group(0))
+            self.root = text.root_from_url(self.url)
         elif domain:
             self.root = text.ensure_http_scheme(domain)