feat:新增功能

1.Dashboard下增加子菜单：Panel、MetricPreview
2.Panel菜单下完成以下功能
   （1）panel列表展示中的新增功能
   （2）panel列表展示中对应记录的删除和修改功能
   （3）Add按钮的新增panel功能
3.MetricPreview菜单完成了左侧列表的跳转功能

nezha-fronted/src/components/page/dashboard/metricPreview.vue

@@ -0,0 +1,49 @@
+<style scoped>
+  .metricPreview {
+    height: 100%;
+  }
+</style>
+<template>
+    <div class="metricPreview">
+        <div class="content-left">
+            <div class="sidebar-title">{{$t('dashboard.title')}}</div>
+            <div class="sidebar-info">
+                <div class="sidebar-info-item sidebar-info-top" @click="jumpTo('panel')">{{$t('dashboard.panel.title')}}</div>
+                <div class="sidebar-info-item sidebar-info-item-active">{{$t('dashboard.metricPreview.title')}}</div>
+            </div>
+        </div>
+        <div class="content-right">
+
+        </div>
+
+    </div>
+
+</template>
+<script>
+export default {
+  name: "metricPreview",
+  data() {
+    return {
+
+    }
+  },
+  methods: {
+    jumpTo(data,id) {
+      this.$store.state.assetData.moduleData = data;
+      this.$store.state.assetData.selectedData = id;
+      this.$router.push({
+        path: "/" + data,
+        query: {
+          t: +new Date()
+        }
+      });
+    }
+  },
+  mounted: function() {
+
+  },
+  watch: {
+
+  }
+}
+</script>