Configure more ElasticsearchSinkOptions through AppSettings

[letargis]

Does this issue relate to a new feature or an existing bug?

• Bug
• New Feature

Please describe the current behavior?
Only limited subset of ElasticsearchSinkOptions properties allowed to configure through AppSettings.

Please describe the expected behavior?
I understand that it is hard to configure properties of Func<>, but I propose to extend number of simple parameters. For my current task I need to manage numberOfShards and numberOfReplicas properties from configuration, so I propose to add to appSettings following properties:

• autoRegisterTemplate
• autoRegisterTemplateVersion
• overwriteTemplate
• numberOfShards
• numberOfReplicas

[mivano]

See my feedback at the PR.