Fix descending order in DHF API calls
Support for descending order in DHF API (former SPS API) has been implemented in different way than in original code supplied by Blocktrades.
Please compare: iterate_results
from database_api.cpp
and iterate_ordered_results
https://github.com/blocktradesdevs/steem/blob/sps-develop-stable/libraries/plugins/apis/sps_api/sps_api.cpp