message: add a epoch_start for each network
diff: pub mod net {
  - use blockchain::{HeaderHash};
  + use blockchain::{HeaderHash,EpochId};
  use wallet_crypto::config::{ProtocolMagic};
  use std::{path::{Path}, fs::{File}};
  use serde_yaml;
  @@ -9,6 +9,7 @@ pub mod net {
  pub domain: String,
  pub genesis: HeaderHash,
  pub protocol_magic: ProtocolMagic,
  + pub epoch_start: EpochId,
  }
  impl Config {
  pub fn mainnet() -> Self {
  @@ -16,6 +17,7 @@ pub mod net {
  domain: "relays.cardano-mainnet.iohk.io:3000".to_string(),
  genesis: HeaderHash::from_hex(&"89D9B5A5B8DDC8D7E5A6795E9774D97FAF1EFEA59B2CAF7EAF9F8C5B32059DF4").unwrap(),
  protocol_magic: ProtocolMagic::default(),
  + epoch_start: 0,
  }
  }
  @@ -24,6 +26,7 @@ pub mod net {
  domain: "relays.awstest.iohkdev.io:3000".to_string(),
  genesis: HeaderHash::from_hex(&"B365F1BE6863B453F12B93E1810909B10C79A95EE44BF53414888513FE172C90").unwrap(),
  protocol_magic: ProtocolMagic::new(633343913),
  + epoch_start: 4,
  }
  }
  