i18n, vue-router and vuex upgrade

1. Configuration of i18n legacy as false.
2. Translation function t is called using the useI18n.
3. Used the i18n.global.t() function from i18n instead of this.$t()
4. Event bus error that occurred during logout.
5. Implemented vue-router 4.4.0 and vuex upgrade to 4.1.0

Change-Id: I9464d82c76dcc1445ce271983ea3ab9d7b03d265
Signed-off-by: Surya Venkatesan <suryav@ami.com>
diff --git a/src/views/Overview/OverviewInventory.vue b/src/views/Overview/OverviewInventory.vue
index 1da5685..4d923e1 100644
--- a/src/views/Overview/OverviewInventory.vue
+++ b/src/views/Overview/OverviewInventory.vue
@@ -30,6 +30,7 @@
 <script>
 import OverviewCard from './OverviewCard';
 import BVToastMixin from '@/components/Mixins/BVToastMixin';
+import { useI18n } from 'vue-i18n';
 
 export default {
   name: 'Inventory',
@@ -37,6 +38,11 @@
     OverviewCard,
   },
   mixins: [BVToastMixin],
+  data() {
+    return {
+      $t: useI18n().t,
+    };
+  },
   computed: {
     systems() {
       let systemData = this.$store.getters['system/systems'][0];