Travis build is not building the docker image

Various issues:
* Travis is not building the docker image, needs to do this and apply all the floating tags (see stroom's build config)
* The doocker context should be move to /docker
* the gradle build needs to unzip the dist zip into the /docker/build
* The dockerfile needs to add the stuff in /docker/build
* need to implement a stroomproxy user, and generally copy what was done for stroom
* may need to expose a volume

Start by inspecting the Travis configuration, Gradle build, Dockerfile, and the existing /docker layout. Compare the build configuration and Docker setup with Stroom, including the dist ZIP extraction and image tags. Done means Travis builds the Docker image with floating tags, the context and build output use the requested paths, and the proxy user and volume behavior are addressed.

Written by the indexing model from the issue text.