feat(docker/node): sovereign node utils

[xendarboh]

Following #54, facilitate self-contained sovereign node that is easily able to join an active network.

• add init target to Makefile.appchain to register local dev network with (local) appchain
• create docker-compose.yml specifically for a single node
• add bash script to start a dockerized node, initializing it from scratch
• use single .env to configure scripts and docker (compose), configure:
  • identifier, port, type, address
  • appchain endpoints
• sane defaults
  • port
  • default node log level to INFO (with easily ability to config to DEBUG)
• support network registration by given network_id