Attempt to make default config more consistent

The general idea here is that config examples should just have a hash and no
extraneous whitespace, both to make it easier for people who don't understand
yaml, and to make the examples stand out from the comments.

synapse/config/password.py

@@ -28,6 +28,7 @@ class PasswordConfig(Config):
     def default_config(self, config_dir_path, server_name, **kwargs):
         return """
         # Enable password for login.
+        #
         password_config:
            enabled: true
            # Uncomment and change to a secret random string for extra security.