What this PR does / why we need it?

• This PR resolves Integrate genesis-generator into axon. #1346.
  => All configurations could be readable.

Currently, genesis-generator has too many hardcode variables,

• axon/devtools/genesis-generator/src/main.rs

  Line 26 in 8815f58

  let input_path = "../chain/genesis_single_node.json";

• axon/devtools/genesis-generator/src/main.rs

  Lines 67 to 69 in 8815f58

  	let path = "./temp";
  	let _ = std::fs::create_dir_all(path);
  	fs::write("./temp/new-genesis.json", output_genesis_str).unwrap();

• axon/devtools/genesis-generator/src/main.rs

  Line 115 in 8815f58

  let input_path = "metadata.json";

  
  and requires all private keys of all nodes.

• axon/devtools/genesis-generator/src/main.rs

  Lines 97 to 102 in 8815f58

  	let mut entries = fs::read_dir(config_path)
  	.unwrap()
  	.filter_map(|res| {
  	res.ok().and_then(|e| {
  	let path = e.path();
  	if path.extension().map(|e| e == "toml").unwrap_or_default() {

• axon/devtools/genesis-generator/src/main.rs

  Lines 124 to 129 in 8815f58

  	let ve_list = entries
  	.iter()
  	.map(|file_name| {
  	let config: Config = parse_file(file_name, false).unwrap();
  	let priv_key = config.privkey;
  	get_ve(Hex::encode(priv_key.as_ref()), propose_weight, vote_weight)

What is the impact of this PR?

BREAKING CHANGE:

• Command line interface

  The sub-command axon run requires a new argument --key $KEY_HEX_STR_WITH_0X_PREFIX or --key-file $KEY_IN_BINARY_FILE, to provided the private key of genesis transactions.