title: Scala Eclipse plugin doesn't show mouse hover documentation
body: <p>I just installed the Scala IDE Eclipse plugin with a fresh install of Eclipse Indigo.  I followed the <a href="http://www.youtube.com/watch?v=PtkNg4mK4NY">getting started youtube video</a> on the scala-ide.org main page on a fresh installation of Indigo. Instead of showing the complete documentation for the String Java class, it shows "type String = String"</p>
  
  <p>I did notice incidentally by looking at the project properties, that in the scala-library.jar and others in the project, under "javadoc location," they show "(None) - non modifiable." I'm not sure if this is the problem, or if the Scala editor gets its documentation somewhere else. </p>
  
  <p>Has anyone else experienced this and/or figured out how to fix it?  Thanks!</p>