title: SoftLayer API SoftLayer_Billing_Item returns resourceTableId property which is not defined in the documentation
body: <p>When I retrieve a SoftLayer_Billing_Item through the SoftLayer API as in the following REST API GET call:</p>
  
  <pre><code>https://api.softlayer.com/rest/v3/SoftLayer_Billing_Item/151376733
  </code></pre>
  
  <p>The result contains all the local properties defined in the SoftLayer Reference Documentation.
  <a href="http://sldn.softlayer.com/reference/datatypes/SoftLayer_Billing_Item" rel="nofollow noreferrer">http://sldn.softlayer.com/reference/datatypes/SoftLayer_Billing_Item</a></p>
  
  <p>The result also returns a property called resourceTableId which is not listed in the documentation.
  The resourceTableId value for the billing item above is 28467033.</p>
  
  <p>If I use that resourceTableId value in a virtual guest API REST call, e.g.,  </p>
  
  <pre><code>https://api.softlayer.com/rest/v3/SoftLayer_Virtual_Guest/28467033
  </code></pre>
  
  <p>I get the details of the resource that generated the billing item.  I have tried other examples including hardware examples and all have worked fine. It's a good way to tie the billing item back to what generated it.</p>
  
  <p>However, I am getting an error when I include the resourceTableId property in a objectMask request. The response says resourceTableId is not a property.</p>
  
  <p>Here's an example querying SoftLayer_Billing_Item with a mask.</p>
  
  <pre><code>https://api.softlayer.com/rest/v3/SoftLayer_Billing_Item/151376733?objectMask=mask[id,hostName,domainName,resourceTableId]
  </code></pre>
  
  <p>comes back with</p>
  
  <pre><code>{
  "error": "Property 'resourceTableId' not valid for 'SoftLayer_Billing_Item'.",
  "code": "SoftLayer_Exception_WebService_ObjectMask"
  }
  </code></pre>
  
  <p>Is there a way to include the resourceTableId in a objectMask request?</p>