Reorder selector properties according to WSDL

[c960657]

The CampaignService requires the selector properties to appear in a specific order.

If i run the example code, the API returns this error:

<soap:Envelope 
  xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Body>
    <soap:Fault>
      <faultcode>soap:Client</faultcode>
      <faultstring>Unmarshalling Error: cvc-complex-type.2.4.a: Invalid content was found starting with element 'fields'. One of '{"https://adwords.google.com/api/adwords/cm/v201605":ordering, "https://adwords.google.com/api/adwords/cm/v201605":paging}' is expected. </faultstring>
    </soap:Fault>
  </soap:Body>
</soap:Envelope> 

This PR orders the selector properties according to the WSDL:
https://adwords.google.com/api/adwords/cm/v201605/CampaignService?wsdl