Input - InitialDataSetPickerF v1.3
Input - InitialDataSetPickerF v1.3

Methods added:
- _create_question_text
- update_picker_id
- form_is_valid

Improvements:
- enable method;
- disable method;
- The form's validity is stored by self._valid.

Others:
- Moved instruction text to input_constants.

dani-i/bachelor-project