updated helm chart to use v5.7.0 and latest PostgreSQL sub-chart (hap…

…ifhir#346)

Feature/update docker support (hapifhir#319)

* Updated docker image according to discussion on hapifhir#305

* Added doc

* Added corrections according to comments

* Update Dockerfile

* Update build-images.yaml

Updated to default to distroless

Merge pull request hapifhir#293 from chgl/updated-helm-chart

updated helm chart to use image v5.6.0

simplified helm chart