Add backup and restore configuration functionality

V2rayNG/app/src/main/res/values-zh-rCN/strings.xml

@@ -173,6 +173,9 @@
     <string name="title_about">关于</string>
     <string name="title_source_code">源代码</string>
     <string name="title_tg_channel">Telegram 频道</string>
+    <string name="title_configuration_backup">备份配置</string>
+    <string name="summary_configuration_backup">备份存储位置: [%s], 卸载App后会备份将被清除</string>
+    <string name="title_configuration_restore">还原配置</string>
 
     <string name="title_pref_promotion">推广</string>
     <string name="summary_pref_promotion">一些推广,点击查看详情(捐赠可去除)</string>