Read application properties from env first and add Docker configuration.

[G8XSU]

• Read application properties from env first.
  Prioritize environment variables over configuration file properties.
  This allows the service to adapt dynamically to different deployment
  environments by overriding config file settings with environment-specific
  values when available.

• Change default war filename to vss.

• Add Docker configuration.
  Add docker-compose and Dockerfile, which spins up a postgres and
  vss instance. We override env variables such as vss.jdbc.url,
  to point to postgres container.