Create blockchain management command

[dmugtasimov]

TODO:

• Command name blockchain
• Subcommands get-block (print block JSON by block number), get-blocks (print range of block JSONs by block numbers), get-blockchain-state (print by block number) (use subparsers)
• Allow --api <network-address> option (use APIBlockchain in that case) -> submit in the second PR, so we can get locally operating management command earlier
• Use def yield_blocks_slice(self, from_block_number: int, to_block_number: int): for both get-block and get-blocks in API mode to save development time (put corresponding TODO to refactor it later)

[olegtropinin]

@dmugtasimov
Could you assign this task to me again after merging of existed PR. I have to implement getting of blocks, range of blocks, blockchain state from API blockchain interface.

[dmugtasimov]

@olegtropinin thank you, merged. I may add some improvements now

[dmugtasimov]

@olegtropinin I decided to rename the command

[dmugtasimov]

@olegtropinin made many changes. let's discuss them tomorrow: #482

I looks like only implementation of get-blockchain-state for remote blockchain is left to do