Add category and sub-category in the job data model

[danse]

This will enable me to perform better analyses

• check the JSON structure and the possibility of writing a test case
• update the data model and the parser
• update opwer-export-data
• try to include the new fields in the pair analysis

[danse]

{
   "profile" : {
      "op_required_skills" : "",
      "op_high_hourly_rate_all" : "0",
      "op_pref_hourly_rate_max" : "",
      "op_tot_cand" : "0",
      "op_job_category_v2" : {
         "op_job_category_v" : {
            "name" : "Illustration",
            "groups" : {
               "group" : {
                  "uid" : "531770282580668421",
                  "name" : "Design & Creative"
               }
            }
         }
      },
      "op_additional_questions" : {