Add hashes to qualifier serilization output

- Adds new option for serilizing snaks with hashes
- Makes SnakSerilizer check for the option
- Makes claim serializer use said option
- Updates json.doc
- Expand Result builder test to test output
  with qualifiers
- Also fix ClaimSerializerTest

Bug: 50570
Change-Id: I3e00aa72bfd64434ecffd597cb6cad542d85a68c