device: show address on device display

- Trezor: support for device address display (subaddress, integrated address)
- Wallet::API support added
- Simplewallet:
  - address device [<index>]
  - address new <label>  // shows address on device also
  - integrated_address [device] <payment_id|address>  // new optional "device" arg to display also on the device

src/device/device_cold.hpp

@@ -47,6 +47,7 @@ namespace hw {
     std::vector<cryptonote::address_parse_info> tx_recipients;  // as entered by user
     boost::optional<int> bp_version;  // BP version to use
     boost::optional<unsigned> client_version;  // Signing client version to use (testing)
+    boost::optional<uint8_t> hard_fork;  // hard fork being used for the transaction
   };
 
   class device_cold {