added drupal documentation and minor fixes

README.txt

rest_api_authentication.info.yml

src/Authentication/Provider/restAPI.php

src/Controller/rest_api_authenticationController.php

src/Form/MiniornageAPIAuthnRequestTrial.php

src/Form/miniorangeAPIAuth.php

src/MiniorangeApiAuthSupport.php

src/advancedSettingsForm.php

src/customerSetupForm.php

src/requestForDemoForm.php

src/setupAuthenticationForm.php

src/upgradePlansForm.php