feat: perfect migrate to @vue/cli-service, upgrade vue babel version

1. update to @vue/cli-service@3.0.5, @babel/core@7.0.0
2. use vue-cli service replace config file in build/ and config/
3. upgrade vue and babel configuration
4. solve the svg-sprite config problem #980

refs: #932 #1087  #980 #1056

src/utils/request.js

@@ -5,7 +5,7 @@ import { getToken } from '@/utils/auth'
 
 // create an axios instance
 const service = axios.create({
-  baseURL: process.env.BASE_API, // api 的 base_url
+  baseURL: process.env.VUE_APP_BASE_API, // api 的 base_url
   timeout: 5000 // request timeout
 })