title: IntelliJ Idea: how to dock the java-doc window
body: <p>how can we dock the <a href="https://www.jetbrains.com/help/idea/2016.2/documentation-tool-window.html" rel="nofollow">java-doc window</a> to the IntelliJ IDE?
  There is no <code>Docked mode</code> in the window-popup like explained in the <a href="https://www.jetbrains.com/help/idea/2016.2/viewing-modes.html#ways_to_control" rel="nofollow">IDE help</a></p>
  
  <p>e.g. it should be like the Structure, Messages, Version Control tool Window.</p>