Small Docker container-related fixes

[evanebb]

• Add more .dockerignore entries to shrink the build context; previously it would send anything in the bin/ folder too, which can be large.
• Fix the database name configuration directive being overwritten by the database host value when environment variables are used instead of command-line flags. Oops.
• Add a 30 second time-out to the database connection check that continuously checks whether the database is reachable instead of just immediately exiting if the initial check fails.
• Print the configured listening address in the logs when starting the API.
• In the Docker Compose file, bump the image tag to the latest release, make the Gobble container dependent on the database container and add some friendlier container names.