Loops and HTTP control server rework (#308)

- CRUD REST HTTP server
- `/v1` HTTP server prefix
- Retrocompatible with older routes (redirects to v1 or handles the requests directly)
- DNS, Updater and Openvpn refactored to have a REST-like state with new methods to change their states synchronously
- Openvpn, Unbound and Updater status, see #287

internal/models/build.go

@@ -3,5 +3,5 @@ package models
 type BuildInformation struct {
 	Version   string `json:"version"`
 	Commit    string `json:"commit"`
-	BuildDate string `json:"buildDate"`
+	BuildDate string `json:"build_date"`
 }