Fix for situation when len(values) is 0. Before fix it will result with
malformed insert query with empty values vector.

- process_hive_post_operation will return post_category,
- post_category will be used to set initial post tag,
- post_category a parent category if parent_author exists
  or parent_permlingif parent_author does not exists.

 Conflicts resolved:
	hive/server/condenser_api/cursor.py
	hive/server/condenser_api/methods.py
	hive/utils/stats.py

Applied account_history_api::enum_virtual_ops new capabilities

See merge request blocktrades/hivemind!7

Merge branch 'dk-issue-3-filtered-vops' of gitlab.syncad.com:blocktrades/hivemind into dk-issue-3-filtered-vops

 Conflicts:
	hive/steem/client.py

- removed "limit":1000 option in enum_virtual_ops call (limit was
  causing trimming ops)
- fixed some syntax errors

Preliminary version using filters in enum_virtual_ops. Some strange porblems occured related to missing payout in comment_reward_operation.

  * added query limit to avoid SQL overflow errors,
  * fixed inefficient insert query, pervious was using selects for each row,
- In apis:
  * subqueries were changed to inner joins

CRITICAL FIX: escaping routine was invalid causing empty values in hive_post_data. Body for get_active_votes

Removed track_tx: it was causing missing COMMIT for START TRANSACTION error. Improved keyboard interruption. Added missing APIs: with placeholders but it will be filled with proper methods. Other minor fixes.

Support for comment_options_operation, percent_steem_dollars renamed to percent_hbd, changed some defaults in schemas, removed percent_steem_dollars column from hive_posts

- Fixed handling of KeyboardInterrupt

- Fixed generation of votes insertion query (missing limit so query exceeded SQL limit). Also simplified SQL code
- comment_payout_op is done via grouped UPDATE query to improve sync performance
- follow insert is done via grouped UPDATE query to improve sync performance
- Implemented statistics gathering for each processed block to print number of processed operations
- virtual ops are prepared in its dedicated thread to improve sync performance
- Added printing of total execution time of sync, at each block-range report.

Merge branch 'dk-issue-3-concurrent-block-query' of gitlab.syncad.com:blocktrades/hivemind into dk-issue-3-concurrent-block-query

Merge branch 'dk-issue-3-concurrent-block-query' of gitlab.syncad.com:blocktrades/hivemind into dk-issue-3-concurrent-block-query

Merge branch 'dk-issue-3-concurrent-block-query' of gitlab.syncad.com:blocktrades/hivemind into dk-issue-3-concurrent-block-query

Resolved Conflicts:
	hive/indexer/posts.py

Simplified queries related to votes processing. Still is needed unification to have one insertion path using ON CONFLICT extension

WIP: Implemented concurrent fetching of blocks and vops to avoid blocking operation processing during API calls.

- Added additional index to hive_posts (indexing single permlink_id field) to speedup insertion
- Removed not needed multi column indices from hive_account table
- Introduced function `process_hive_post_operation' covering new-post, post-edit, post-undelete scenarios in single query at SQL side
- Introduced function `delete_hive_post' to simplify post deletion at client side and improve performance.
- Improved reblog operation queries (eliminated separate queries for IDs to be next processed/updated)
- Improved follow operation queries (eliminated separate queries for IDs to be next processed/updated). Prerequisites for value caching and flush at Python side, not finished yet