title: Phing Property in property file should contain multiple values
body: <p>As far as I know it is not posssible to have an array of values in a property file.
  What would be the best solution to store multiple values in a property?</p>
  
  <p>e.g. part of property file</p>
  
  <pre><code># directory definitions 
  # containing e.g. CSS, Javascript, ...
  project.dirname_css = css
  project.dirname_js = javascript
  </code></pre>
  
  <p>What I want is an array of properties like:</p>
  
  <pre><code># directory definitions 
  # containing e.g. CSS, Javascript, ...
  project.dirname_css = [css,portal_specific]
  project.dirname_js = [javascript,portal_specific]
  </code></pre>
  
  <p>to loop them in the build.xml<br>
  Any suggestions how to do this?<br>
  I could imagine to do divide values by ; and explode them in the build.xml.
  Any better suggestions?</p>