Ms all block api methods

Implemented methods hive.get_block and hive.get_block_range. Works bot for reversible and irreversible, get_block_range is limited to 1000 blocks - as in block_api. There is large performance difference between blocks irreversible and reversible (for reversible is like x5 time slower). Its seems that performance for reversible could be further improved, this requires review of blocks_views_for_head_block.sql - looks like views are bottleneck here