- 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

More improvements: readability improved, added matarialized view from upgrade script, removed _get_parent_by_child_id

[WIP] Native votes support: removed votes columns from migration script and schema, added conversion routine to convert old votes format (as text blob) to hive_votest table