Unable to set custom annotations on ES cluster and associated resources via elasticsearch chart

[dwhitlow]

Adding support for a value for custom annotations would be useful for specifying things like cost products/teams and standardized k8s operators such as app.kubernetes.io/instance.

Here's an example of this from one of Helm's community charts: https://github.com/helm/charts/blob/master/stable/redis/templates/redis-master-statefulset.yaml#L31