Standarize unbound, prepare for setup inclusion

- Use jinja template for configuration file (start.py)
- Limit access to the Mailu subnet
- Implement health checks

services/unbound/start.py

@@ -0,0 +1,9 @@
+#!/usr/local/bin/python3
+
+import jinja2
+import os
+
+convert = lambda src, dst: open(dst, "w").write(jinja2.Template(open(src).read()).render(**os.environ))
+convert("/unbound.conf", "/etc/unbound/unbound.conf")
+
+os.execv("/usr/sbin/unbound", ["-c /etc/unbound/unbound.conf"])