Major refactor to make handling name/path manipulation easier.

Most of this is now in doom_base.py, which stores wad/map/name, exposes them as
properties, and also takes care of most common tasks needed for building
command lines and such.

dcc/ss.py

@@ -29,7 +29,7 @@ class SS(dcc.doom_base.WadMap):
 						sys.exit("Gave up on image verification")
 					if not accepted:
 						return False
-				img.save(filename=dcc.config.BaseThumbPath(parsed_args.wad, parsed_args.map, parsed_args.name))	
+				img.save(filename=self.base_thumb_path())	
 				return True
 
 		while not try_screenshot():