Fill in the blanks: add "dropdowns" to Quiz

As an author
I want dropdowns to be presented in courses that are based on Quiz template,
so I can check knowledge/behaviour change of my learners using the blanks with predefined list of answer options.

CoA:
- Learner can choose one of the possible answers from a dropdown and get the appropriate score/feedback for all the submitted questions in courses that are based on Quiz template

Note: xAPI answered statement should consider dropdowns