优化商品的多属性的下拉框，增加刷新按钮

jshERP-web/src/views/material/modules/MaterialModal.vue

@@ -163,6 +163,12 @@
                   <a-tooltip title="多属性针对服装、鞋帽、家纺等行业（注意不要勾选多单位，因为多属性商品不支持多单位，只支持单个的单位）">
                     <a-select mode="multiple" v-decorator="[ 'manySku' ]" showSearch optionFilterProp="children"
                       placeholder="请选择多属性（可多选）" @change="onManySkuChange" :disabled="attributeStatus">
+                      <div slot="dropdownRender" slot-scope="menu">
+                        <v-nodes :vnodes="menu" />
+                        <a-divider style="margin: 4px 0;" />
+                        <div style="padding: 4px 8px; cursor: pointer;"
+                             @mousedown="e => e.preventDefault()" @click="initMaterialAttribute">没找到？点此刷新列表 <a-icon type="reload" /></div>
+                      </div>
                       <a-select-option v-for="(item,index) in materialAttributeList" :key="index" :value="item.value" :disabled="item.disabled">
                         {{ item.name }}
                       </a-select-option>