Fix permissions when running dev container as non-root user

I wanted to pass `—user` to `docker-compose` up, but that option doesnt exist. To get around this, I had to record the uid on the host (CURRENT_UID), interpolate the variable in tools/docker-compose.yml, and detect that inside the container. I then piggy-backed on the /etc/passwd hack we use for scenarios with unpredictable uids.

tools/docker-compose/nginx.conf

@@ -1,4 +1,3 @@
-user  nginx;
 worker_processes  1;
 
 error_log  /var/log/nginx/error.log warn;