警告:scene is unreachable due to lack of entry points and does not have an identifier
表題のような警告が出た場合の対処法は
「Storyboard IDを入力する」
参考資料
http://kmacs1.blogspot.jp/2013/01/scene-is-unreachable-due-to-lack-of.html
http://santa20.com/index/tag/storyboard(Storyboard IDの設定方法)