title: create incident through webservice in servicenow not creating incident number
body: <p>I am creating an incident via web service by reading incident json data from a txt file. The incident gets created but the incident number field is empty in the generated incident in my instance(Fiji). I am setting the incident number in the input json data. I wanted to know if we can specify the incident number in the input json data or have the table auto generate the incident number. 
  Regards,
  Priyank</p>