Add logic to muzima core module to only allow forms with proper discriminator tagged as 'registration'

mUzima identifies forms as registration forms by checking whether they have 'registration' tag. On the other hand while saving and uploading form data from device side, and processing the data at server side, identification is based on form discriminator.

For instance, the HTML registration form must be tagged 'registration' and must be set with the discriminator 'json-registration'.

If a form is tagged as 'registration' and it does not have proper discriminator, it leads to inconsistencies dealing with form data at device side, which causes errors.

There's need to add logic/validation to mUzima core module to ensure that 'registration' tag is applied to forms with proper discriminator.

Testing criteria:

• Using advanced setup wizard, the app should accept a form as registration form whether it has 'registration' tag or not, provided the form has a registration discriminator set at server side.
• The app should fail to proceed with the setup process as long as no form with registration discriminator is selected.
• The patient registration work flow should remain as currently expected.