- Add ubuntu-18.04
- add pkg-config to ubuntu(s)
- Rework Docker Makefile
- Add test job to verify archive
- Add cc.Dockerfile
- Add java.Dockerfile
- Add dotnet.Dockerfile
- Build ortools in docker_<lang>
- Build archive and fz_archive in two separate containers
- Add dependencies to makefiles when building docker image
- Suppress previous archive if any
- Improve docker build by using export/archive when building language images
- Reduce build context using export/$* instead of .
note: when running `docker build ... foo`, all files in `foo` are recursively
send to the docker daemon before building. Since we have tons of Go of images
it could take time to "upload".
