Added 'Create Application', 'Create Application&Registration' and required auxiliary functions

Included in this merge request:

• option to create applications

Includes auxiliary functions in order to be able to create managed applications on the Application Portal, similar to what is done by the AuthzOperator.

• requirements.txt

To facilitate the usage of the library by any environment.

Example usage:

python3 create_application_and_registration.py --client webdfs-application-manager --secret <My_Secret> --ownerUPN fborgesa --appId test-app-creation --appName test-app-creation --resourceCategory Test --baseURL https://fborgesa.webtest.cern.ch --redirections https://fborgesa.webtest.cern.ch/*