Bank Details in an organisation.

Work done in gkcore.

In api_organisation.py file.

  1)  written a code in "GET" if bankdetails are available. it will show the data. the details are in dictionary form that is key & value.

  2)  written a code in "PUT" for saving null values of bankdetails and update in database.

  3) details are shown in database. 

Closes #863