title: Shortcut to mark directory as source
body: <p>In the current use case with intellij-idea 13.1.1, I try to only use the keyboard.<br>
  * I go in my project structure - Alt+1<br>
  * I create a "java" directory - Alt+insert<br>
  * I want to mark this directory as a source directory  ???</p>
  
  <p>There is a menu item in the contextual menu: "Mark directory as"...<br>
  But I don't know how to invoke it from the keyboard.</p>
  
  <p>Is it possible?</p>