title: Prevent multiple instances of Eclipse RCP Application
body: <p>I'd like to make an RCP application that only opens once.</p>
  
  <p>If you open it again, it focuses (ideally passing through the arguments supplied) on the original window.</p>
  
  <p>My use-case involves multiple concurrent users (with their own user accounts) on the same computer, so I don't think the route of opening a port would work.</p>
  
  <p>I'm using RCP4 - a lot of the existing stuff I've seen online is RCP3 or older.</p>