removing some more edx specific info from the sandbox template

also adding comments

playbooks/secure_example/vars/edxapp_sandbox.yml

@@ -12,7 +12,15 @@
 #
 #  You must fill in credentials for sending
 #  mail using AWS
-
+#
+#  Set the following before using this configuration
+#  configuration.
+#   
+#    * AWS_ACCESS_KEY_ID
+#    * AWS_SECRET_ACCESS_KEY
+#    * SESSION_COOKIE_DOMAIN
+#    * FEEDBACK_SUBMISSION_EMAIL
+#
 #Use YAML references (& and *) and hash merge <<: to factor out shared settings
 #see http://atechie.net/2009/07/merging-hashes-in-yaml-conf-files/
 
@@ -70,7 +78,7 @@ generic_auth_config:  &generic_auth
     'url':  ''
  
 generic_env_config:  &generic_env
-  'BOOK_URL':  'https://mitxstatic.s3.amazonaws.com/book_images/'
+  'BOOK_URL':  ''
   'CERT_QUEUE':  'certificates'
   'LOCAL_LOGLEVEL':  'INFO'
   'MITX_FEATURES':
@@ -87,7 +95,7 @@ generic_env_config:  &generic_env
   'LOG_DIR':  '/mnt/logs/edx'
   'MEDIA_URL':  ''
   'ANALYTICS_SERVER_URL':  ''
-  'EEDBACK_SUBMISSION_EMAIL': 'bugs@edx.org'
+  'FEEDBACK_SUBMISSION_EMAIL': ''
   'TIME_ZONE': 'America/New_York'
   'CACHES':  &lms_caches
     'default':
@@ -119,7 +127,7 @@ generic_env_config:  &generic_env
   'CELERY_BROKER_HOSTNAME': ''
   'COMMENTS_SERVICE_URL':  ''
   'LOGGING_ENV':  'sandbox'
-  'SESSION_COOKIE_DOMAIN':  'amazonaws.com'
+  'SESSION_COOKIE_DOMAIN': !!null
   'COMMENTS_SERVICE_KEY':  ''
 lms_auth_config:
   <<: *generic_auth