title: Rally waspi queries - filter using 'in' operator
body: <p>I was trying to get all of the user stories associated with a given rollup by querying first for the features that have that rollup as their parent, and then finding all of the stories that have that feature as their PortfolioItem parent.</p>
  
  <p>However, this requires some messy looping in order to loop over all of the features to get their children.  I have been using multiple WSAPI data stores for my queries, and I want to use some of the syntax from the lbapi queries - particularly, can you use the 'in' value as an operator?  I tried doing that with an array of ids supplied, but it did not appear to work.  I would be much more elegant (and easier) to do something like</p>
  
  <pre><code>filters : [{
      property : 'Parent.ObjectID',
      operator : 'in',
      value    : ids
  }]
  </code></pre>
  
  <p>rather than</p>
  
  <pre><code>Ext.Array.each(ids, function(id) {
      ...
      filters : [{
          property : 'Parent.ObjectID',
          operator : '=',
          value    : id
      }]
  </code></pre>
  
  <p>Or is this unique to the LBAPI?  Am I going about this in entirely the wrong way? Thanks</p>