title: Xtext: formatting rule with no hidden terminals removes whitespaces
body: <p>In my Xtext grammar I have a rule which doesn't have hidden terminals e.g. </p>
  
  <pre><code>Model:
      greetings+=Greeting*;
  
  Greeting:
      'Tag' (tags+=HashTag)+ ';';
  
  HashTag hidden():
      '#' name=ID 
  ;
  </code></pre>
  
  <p>All is working well, but when I format my file content (Shift+Alt+F) the spaces between HashTags are removed which creates one long HashTag...
  E.g.
  <code>Tag #a #b #c;</code> -> <code>Tag #a#b#c ;</code></p>
  
  <p>Any help?</p>