Add support for annotations in Service and Webhook config

[ccremer]

Summary

• Adds service.annotations and webhook.annotations parameters to values.yaml
• Adds instructions in README to set up certificate provisioning for OpenShift 4

Checklist

• [x] Categorize the PR by setting a good title and adding one of the labels: bug, enhancement, documentation, change, breaking, dependency as they show up in the changelog
• [x] PR contains the label area:chart
• [x] PR contains the chart label, e.g. chart:provider-postgresql
• [x] Variables are documented in the values.yaml using the format required by Helm-Docs.
• [x] Chart Version bumped if immediate release after merging is planned
• [x] I have run make chart-docs
• [x] Link this PR to related code release or other issues.

[ccremer]

(PR currently is based on #81 , to be rebased later)

[zugao]

Sry i was a bit late to the party, Just finished reviewing and doing some helm templating. LGTM