title: gradle-experimental:0.1.0 buildConfigField
body: <p>Anyone know how to define <code>buildConfigField</code> in the experimental gradle plugin?</p>
  
  <pre><code>android.productFlavors {
      create("demo") {
          applicationId = 'com.anthonymandra.rawdroid'
          buildConfigField "String", FIELD_META, PROVIDER_META
      }
  </code></pre>
  
  <p>gives:</p>
  
  <blockquote>
    <p>Error:Attempt to read a write only view of model of type
    'java.lang.Object' given to rule 'model.android.productFlavors'</p>
  </blockquote>