Environment variables should be used for all configuration

[aromanielloNTIA]

Right now, there are two configuration bits which are not handled through environment variables:

1. The shm_size shared memory setting for the API container
2. The disk device /dev/nvme0n1 used by the API container

Environment variables should be added to env.template to control these. Aside from these two things, all configuration takes place in the env file.