Specify container dependencies in docker compose instructions

[dennisvang]

The fdp-client depends on the fdp, which, in turn, depends on both the relational database (mongo or postgres) and the (optional) triple store.

These dependencies between docker containers need to be specified in the docker compose examples.

For this to work properly, we should also implement health checks for the fdp, relational db, and triple store.

See example in FAIRDataTeam/FAIRDataPoint-E2E-Tests#12