generate docker compose files for federated execution

[housengw]

make sure tests pass after adding code generation for docker compose.
This branch is branched from #750

Also, I will try to refactor CGenerator.doGenerate() since it currently has about 500 lines.

[Soroosh129]

I think this looks great!

In the interest of a more modular design, it would be great if the docker-related functions were in a separate CDockerGenerator.java class (following the naming convention of the Cpp and TS generators).

[lhstrh]

@housengw could you please provide a bit more explanation on what this PR is meant to achieve?

[housengw]

This PR is meant to autogenerate docker-compose.yml files upon calling lfc on containerized federated lf programs. The purpose of docker-compose.yml files is to help ease the deployment of multiple docker containers. The user could do docker compose up in the directory where docker-compose.yml is located and the instruction in the yaml tells docker how to build and run the containers. Without the yaml, the user will have to build and run the an image for each federate manually.