Add Network policy to allow connections from user namespace

[ccremer]

Summary

• Deploys a NetworkPolicy that allows the creator of an instance to connect to the deployed PostgreSQL pod.

Note: In local env with kind this is untestable since kind's default networkplugin doesn't support network policies, so the access works from any namespace. However, I tested the rendered NetworkPolicy from the chart in an OpenShift 4 cluster and it works as expected with the values given in this PR.

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:operator
• [x] Link this PR to related issues
• [x] I have not made any changes in the charts/ directory.

[ccremer]

Note: PR currently is based on #57 , will rebase after is has been merged.