correct yt link

Docker improvements

- Run onionr by default rather than bash
- Run as unprivileged user by default instead of root
- Use /app for all code
- Specify python 3.7 (3.8 fails to build cffi)
- Use apt-get rather than apt (apt's CLI is not stable)
- Slight reformatting and consolidation

Added custom port and bind address args

static-data/default_config.json

@@ -8,6 +8,7 @@
     "general": {
         "allow_public_api_dns_rebinding": false,
         "announce_node": true,
+        "bind_address": "",
         "dev_mode": false,
         "display_header": true,
         "ephemeral_tunnels": false,