Rework of vops and other fixes

hive/db/schema.py

hive/indexer/blocks.py

hive/indexer/posts.py

hive/indexer/votes.py

hive/server/bridge_api/objects.py

hive/server/common/objects.py

hive/server/condenser_api/objects.py

hive/server/database_api/methods.py

hive/server/tags_api/__init__.py

hive/server/tags_api/methods.py

hive/steem/client.py

hive/steem/http_client.py

hive/utils/stats.py

scripts/update_hivemind_db.sql