Add configuration tag

[jrunu]

To facilitate the use of the role to push just configuration changes tags are added at the appropriate locations.

I don't know if there are some ansible community internal default "tags" for a use case like this. Maybe graylog_configuration would be a better name for the tag?

[malcyon]

That's a good idea. The only tags I see in the Ansible docs that are reserved are always and never, so I think configuration is probably fine.