descriptors mapping and set iarc descriptors on response (bug 935679)

- Create mapping from IARC response's descriptor names to our descriptor names.
- Maps their native language descriptor names to our RatingDescriptors field names (e.g. esrb -> blood -> has_esrb_blood)
- Set descriptor on their response from the IARC get app info form.
- Found that order doesn't matter in the descriptors/interactives constants since no signatures.