Create onboarding modal [Fixes #76917104]

![screenshot 2014-08-28 19 05 56](https://cloud.githubusercontent.com/assets/1783869/4084343/e94943f4-2f07-11e4-8c46-5a05538f6e31.png)

ping @fatihacet 
I am asking this because `IDE.AppController` has tons of methods in it and I don't want to add one more if it's not really necessary.