message: add a way to get account number
diff: @@ -83,9 +83,9 @@ impl Account {
  Ok(Account(account))
  }
  + pub fn get_account_number(&self) -> u32 { self.0 }
  pub fn get_scheme_value(&self) -> u32 { self.0 | 0x80000000 }
  -
  pub fn change(&self, typ: AddrType) -> Result<Change> {
  match typ {
  AddrType::Internal => self.internal(),
  