switch to viper for configuration and use cobra for cli

sftpgo.json

@@ -0,0 +1,34 @@
+{
+  "sftpd": {
+    "bind_port": 2022,
+    "bind_address": "",
+    "idle_timeout": 15,
+    "max_auth_tries": 0,
+    "umask": "0022",
+    "banner": "SFTPGo",
+    "upload_mode": 0,
+    "actions": {
+      "execute_on": [],
+      "command": "",
+      "http_notification_url": ""
+    },
+    "keys": []
+  },
+  "data_provider": {
+    "driver": "sqlite",
+    "name": "sftpgo.db",
+    "host": "",
+    "port": 5432,
+    "username": "",
+    "password": "",
+    "sslmode": 0,
+    "connection_string": "",
+    "users_table": "users",
+    "manage_users": 1,
+    "track_quota": 2
+  },
+  "httpd": {
+    "bind_port": 8080,
+    "bind_address": "127.0.0.1"
+  }
+}