Add the ability to consume the Registration Authority Credentials
Add validation to the nullOrString properties
Make expression simpler by using method
Remove NotBlank validator for boolean values
Handle 404 when requesting RA credentials
Update docs to reflect last change
Merge pull request #9 from SURFnet/feature/consume-ra-credentials-api

Add the ability to consume the Registration Authority Credentials API
Merge branch 'develop' into feature/ra