This release
- removes all projects except base-alpine, base-debian, k8s-dataflow
- removes 1 directory per image version approach, to make Dockerfiles source of truth -- git tags will point to specific image versions
- updates CI/CD to introduce stricter checks and linting to comply with best practices
- migrate from Travis to GH Actions
- migrate from Bintray to Docker Hub
- migrate k8s-dataflow image to JDK11