vue_visgraph: add a mechanism to force update component

cfr. https://medium.com/emblatech/ways-to-force-vue-to-re-render-a-component-df866fbacf47

src/Bundle/ChillPersonBundle/Resources/public/vuejs/VisGraph/App.vue

@@ -66,6 +66,11 @@ export default {
 
          // Instanciate vis objects in window variables, see vis-network.js
          window.network = new vis.Network(this.container, this.visgraph_data, window.options )  // A
+      },
+      forceUpdateComponent() {
+         console.log('forceUpdateComponent - method 3')
+         this.$forceUpdate()
+         this.refreshNetwork
       }
    }
 /*