Added correct handling of current_height with respect to genesis_block to blockchain::schema .
Added correct handling of current_height with respect to genesis_block to blockchain::schema .

exonum/exonum,alekseysidorov/exonum,alekseysidorov/exonum,alekseysidorov/exonum,exonum/exonum,alekseysidorov/exonum,exonum/exonum,exonum/exonum