Build docker image using some incremental versioning system

Currently travis is using the build id. Find a way to use the version from the build.gradle file.

Find a way to increase the version in the build.gradle file automatically.

Start by reading build.gradle and the Travis configuration that currently supplies the build ID for the Docker image. Determine how the version in build.gradle should be incremented automatically and how that value should flow into image versioning. Done means the build uses the Gradle version rather than the Travis build ID and reliably increments it.

Written by the indexing model from the issue text.