make 'path' and 'keywords' available in logging messages

Wrap all loggers used by job, extractor, downloader, and postprocessor
objects into a (custom) LoggerAdapter that provides access to the
underlying job, extractor, pathfmt, and kwdict objects and their
properties.

__init__() signatures for all downloader and postprocessor classes have
been changed to take the current Job object as their first argument,
instead of the current extractor or pathfmt.

(#574, #575)

gallery_dl/postprocessor/compare.py

@@ -14,8 +14,8 @@ import os
 
 class ComparePP(PostProcessor):
 
-    def __init__(self, pathfmt, options):
-        PostProcessor.__init__(self)
+    def __init__(self, job, options):
+        PostProcessor.__init__(self, job)
         if options.get("action") == "enumerate":
             self.run = self._run_enumerate
         if options.get("shallow"):