Headless Gamma Docker Image builds the project at runtime

[arminzavada]

When starting the Docker Image it first downloads a lot of maven dependencies, then compiles the project. This is wasteful and unnecessary in the least, and at the worst case results in unrunnable containers; when the given user is not able to write to the ~/.m2 folder.

Please, change the Dockerfile to build images that have only the runnable .jar file, and run it as an entrypoint.

Note: it would also be great, if we could have less image layers (it has currently 31 layers, and is 1.19GB, which is unnecessarily big)

• download theta beforehand, not during the image build process
• use smaller base image (maven should not be needed, niether is a lot of apt-get commands)