Implement Docker image building and publishing for deployment

[maltezacharias]

Switch deployment process to publishing of ready-built docker containers to e.g. DockerHub or a private registry.

• [ ] Create build scripts to create and push new containers
• [ ] Implement automatic image building and pushing process using a suitable mechanism (Travis? DockerHub automated builds?)
• [ ] Investigate whether we should use docker image signing for this?
• [ ] Design a workflow where pushing to a designated protected branch on github will result in an automatic building and deployment of the branch