Refactor docker documentation

This MR refactors the documentation:

• remove unmaintained docker-compose.yml example files
• move nginx reverse proxy to separate file
• fix some typos in docker README
• fix become smith steps
• rename "rpc" nodes to "mirror" nodes

docker/compose/gdev-mirror.docker-compose.yml

-# This is a docker template for running a gdev mirror
-
-version: "3.5"
-
-services:
-  duniter-rpc:
-    image: duniter/duniter-v2s:latest
-    restart: unless-stopped
-    ports:
-      # telemetry
-      - 127.0.0.1:9615:9615
-      # rpc
-      - 127.0.0.1:9933:9933
-      # rpc-ws
-      - 127.0.0.1:9944:9944
-      # p2p
-      - 30333:30333
-    volumes:
-      - ./node.key:/etc/duniter/node.key
-      - duniter-rpc-data:/var/lib/duniter/
-    environment:
-      - DUNITER_CHAIN_NAME=gdev
-      # SERVER_DOMAIN should be replaced by a domain name that point on your server
-      - DUNITER_PUBLIC_ADDR=/dns/${SERVER_DOMAIN?SERVER_DOMAIN should be set}/tcp/30333/ws
-
-volumes:
-  duniter-rpc-data: