Added auth_class and auth_class_parameters

The auth_class and class_parameters options in kippo.cfg can be used to
enable an alternative class (instead of UserDB) for checklogin() in auth.py

kippo.cfg.dist

@@ -69,6 +69,24 @@ filesystem_file = fs.pickle
 # (default: data_path)
 data_path = data
 
+# Class that implements the checklogin() method.
+# 
+# Class must be defined in kippo/core/auth.py
+# Default is the 'UserDB' class which uses the password database.
+#
+# Alternatively the 'AuthRandom' class can be used, which will let
+# a user login after a random number of attempts.
+# It will also cache username/password combinations that allow login.
+#
+auth_class = UserDB
+# When AuthRandom is used also set the 
+#  auth_class_parameters: <min try>, <max try>, <maxcache>
+#  for example: 2, 5, 10 = allows access after randint(2,5) attempts
+#  and cache 10 combinations.
+#
+#auth_class = AuthRandom
+#auth_class_parameters = 2, 5, 10
+
 # Directory for creating simple commands that only output text.
 #
 # The command must be placed under this directory with the proper path, such