feat(docker/node): dockerized node and appchain-pki network

[xendarboh]

• Build and install all relevant binaries used by a node.
• Use the resulting docker image for the local pki=appchain network.
  • use Makefile to build the node docker image
  • separate Makefile.appchain alongside default Makefile
  • remove pki=appchain from Makefile
  • node startup mimics production deployment while supporting local dev
    • use docker volume to pass network.yml to each container
    • use docker volume for common data dir (configs, logs, etc)
    • each node generates their own config for local test network, generate all node configs and single docker-compose.yml
    • ?: create entry.sh script
• docker-compose.yml: set docker user
• docs(docker): update README
• docs: add example .env file
• feat(genconfig): save gateway-specific client files to unique directory: <identifier>-client(2)
  • (too intrusive for now, only applies to whole system config)
• feat(genconfig): use absolute path for auth's (Gateways|Mixes|ServiceNodes).IdentityPublicKeyPem
• feat(genconfig): add option -binary-prefix
  • like -binary-suffix
  • use it to set full path to installed ServiceNode plugin binaries
• feat(genconfig): configure http_proxy ServiceNode plugin
• feat: dynamic run-time http_proxy_config.toml
  • not part of Docker image
  • located in node's data-dir
  • genconfig can create an empty stub file, so the docker image is still functional by default