Set up base build system with Gitlab

[russleyshaw]

• [ ] Setup Gitlab Runners to be easily registered with GitLab given registration token
• [ ] Provide .gitlab-ci.yml to create .tar'd docker images from built client code
• [ ] Add .tar'd data to CI artifacts

Notes: Images should be built in docker environments

It might be best to add the .gitlab-ci.yml to SIG-Game Client Repos too

[russleyshaw]

https://docs.gitlab.com/ce/ci/