Fixes #161, some bugs with non-8000 port

[dconathan]

Makes it so if you specify a different NEXT_BACKEND_GLOBAL_PORT in docker_up.sh, those changes carry through the appropriate places in the docker-compose.yml file.

One thing is to note is that one has to manually set the NEXT_BACKEND_GLOBAL_PORT environment variable when launching an experiment (still defaults to 8000), since presumably that it is in a new environment. We could fix this by making a separate setup.sh or config.sh script that sets all the environment variables, which docker_up.sh and experiment_triplet.py, etc. could then source...

[dconathan]

Hold off on merging this until we discuss #161...

[stsievert]

We also need to hold off merging because of #154 in which we delete experiment_triplet.py and move to a new endpoint for initializing the examples.

From the files changed I can't tell what happens when NEXT_BACKEND_GLOBAL_PORT isn't defined in docker_up.sh. It looks like if the environment variable isn't defined the browser will try to render localhost:.

[dconathan]

Right didn't think about that... if not defined in docker_up.sh, next.constants will still grab the default localhost:8000 but docker-compose.yml will be all effed up.

[dconathan]

This is out of date and conflicts with #166. closing