Rewrite of the entrypoint in Golang (#71)

- General improvements
    - Parallel download of only needed files at start
    - Prettier console output with all streams merged (openvpn, unbound, shadowsocks etc.)
    - Simplified Docker final image
    - Faster bootup
- DNS over TLS
    - Finer grain blocking at DNS level: malicious, ads and surveillance
    - Choose your DNS over TLS providers
    - Ability to use multiple DNS over TLS providers for DNS split horizon
    - Environment variables for DNS logging
    - DNS block lists needed are downloaded and built automatically at start, in parallel
- PIA
    - A random region is selected if the REGION parameter is left empty (thanks @rorph for your PR)
    - Routing and iptables adjusted so it can work as a Kubernetes pod sidecar (thanks @rorph for your PR)

.devcontainer/docker-compose.yml

@@ -0,0 +1,15 @@
+version: "3.7"
+
+services:
+  vscode:
+    image: qmcgaw/godevcontainer
+    volumes:
+      - ../:/workspace
+      - ~/.ssh:/home/vscode/.ssh:ro
+      - ~/.ssh:/root/.ssh:ro
+      - /var/run/docker.sock:/var/run/docker.sock
+    cap_add:
+      - SYS_PTRACE
+    security_opt:
+      - seccomp:unconfined
+    entrypoint: zsh -c "while sleep 1000; do :; done"