Create marc21 record

[philippgualdi]

PR notes

Aim
Provide a rest-api can create marc21 records

Demo
Creating a record

`$ curl -X POST -k -H 'Content-Type: application/json' -i 'https://127.0.0.1:5000/api/marc/' \
--data '{{
   "__order__":[
      "control_number_identifier",
      "date_and_time_of_latest_transaction",
      "physical_description_fixed_field_general_information",
      "fixed_length_data_elements",
      "cataloging_source",
      "language_code",
      "country_of_publishing_producing_entity_code",
      "title_statement"
   ],
   "control_number_identifier":"AT-OBV",
   "date_and_time_of_latest_transaction":"20170703041800.0",
   "physical_description_fixed_field_general_information":"cr#|||||||||||",
   "fixed_length_data_elements":"100504|1932####au######o#####|||#|#ger#u",
   "cataloging_source":{
      "__order__":[
         "original_cataloging_agency",
         "language_of_cataloging",
         "modifying_agency",
         "description_conventions"
      ],
      "modifying_agency":[
         "TUW"
      ],
      "original_cataloging_agency":"TUG",
      "language_of_cataloging":"ger",
      "description_conventions":[
         "rakwb"
      ]
   },
   "language_code":[
      {
         "__order__":[
            "language_code_of_text_sound_track_or_separate_title",
            "translation_indication",
            "source_of_code"
         ],
         "language_code_of_text_sound_track_or_separate_title":[
            "ger"
         ],
         "translation_indication":"No information provided",
         "source_of_code":"MARC language code"
      }
   ],
   "country_of_publishing_producing_entity_code":{
      "__order__":[
         "iso_country_code"
      ],
      "iso_country_code":[
         "XA-AT"
      ]
   },
   "title_statement":{
      "__order__":[
         "title",
         "statement_of_responsibility",
         "title_added_entry"
      ],
      "statement_of_responsibility":"hrsg. von Josef Frank",
      "title":"<<Die>> Internationale Werkbundsiedlung Wien 1932",
      "title_added_entry":"No added entry"
   }
}'
`


Now we can search in the /api/marc/ endpoint to see a list of records:

`$ curl -k "https://127.0.0.1:5000/api/marc/?prettyprint=1"`

[mb-wali]

PR based -

1. consider resolving the conflicts.
2. PR description - format the JSON
3. add more information on why MARC21_UI_EXPORT_FORMATS was removed.

code base -
@utnapischtim and @philippgualdi we should talk over a meeting - and discuss in details the purpose of these changes.
for example why we have a new endpoint? what is the overall purpose of this module?

[utnapischtim]

@philippgualdi does the order key has to be there?