[ABW]: various fixes in database_api responses:

added total_vote_weight column and code filling it with data from updated hived (removed last subquery execution from database_api responses)
added dynamic calculation of abs_shares in hive_posts_view over use of unfilled column of hive_posts (might be changed if we start filling the column)
incoming reward values are no longer cast to INT8, but BIGINT instead
last_payout is no longer passed as not set when post was not yet fully paid
abs_rshares is properly 0 after final payout, vote_rshares are properly sum of all positive rshares