Documentation: Add a note to the Remote Elasticsearch configuration KB mentioning compatible configuration for Shield

The Install And Configure A Remote Elasticsearch Instance page mentions the following parameter is required in elasticsearch.yml:

action.auto_create_index	false

We also mention that Elastic's Shield plugin can be used for security, however users of the Shield plugin may discover that our recommended configuration will prevent Elasticsearch from starting up - action.auto_create_index can't be set to false when using the Shield plugin or Elasticsearch will fail to start.

Bearing in mind this is a third party plugin, since many customers may elect to choose this option can we add a small note to the recommended elasticsearch.yml configuration as follows:

Third party plugins, such as Elastic's Shield plugin, may require specific exceptions to be set for action.auto_create_index. Please consult your provider's documentation for more information.