replace old children count

previously method does not work for block range different than all blocks

• add block_num_created column for hive_posts table, it is required to distinguish between post create and post update events in given block range
• both root and non-root posts have updated block_num when are edited
• when post is edited his block_num is also updated

added 4 commits

• 2e7fb2d3...917c7f73 - 3 commits from branch develop
• 0e3c8700 - replace old children count

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added 1 commit

• 8d710de2 - fully deterministic mentions order

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merged

mentioned in commit 47a50445

mentioned in issue #82 (closed)