Enable PROXY procotol for proxy hosts

frontend/js/models/proxy-host.js

@@ -19,6 +19,8 @@ const model = Backbone.Model.extend({
             hsts_subdomains:         false,
             caching_enabled:         false,
             allow_websocket_upgrade: false,
+            enable_proxy_protocol:   false,
+            load_balancer_ip:        '',
             block_exploits:          false,
             http2_support:           false,
             advanced_config:         '',