title: How configure packages.config to download the highest version
body: <p>I want to configure packages.config to download the available highest version of a package. How can I do that?</p>
  
  <p>Something like:</p>
  
  <pre><code>&lt;package id="PackageName" version="Highest" ... /&gt;
  </code></pre>
  
  <p>I saw attr "allowedVersions", but it always download the version configured in "version" attr.</p>