device: enable to use multiple independent device wallets

- adds a new option `--hw-device-deriv-path` to the simple wallet. Enables to specify wallet derivation path / wallet code (path avoided so it can be misinterpreted as a file path).
- devices can use different derivation mechanisms. Trezor uses standard SLIP-10 mechanism with fixed SLIP-44 prefix for Monero
- Trezor: when empty, the default derivation mechanism is used with 44'/128'/0'. When entered the derivation path is 44'/128'/PATH.
- Trezor: the path is always taken as elements are hardened (1<<31 bit turned on)

src/device/device.hpp

@@ -138,6 +138,7 @@ namespace hw {
 
         virtual device_protocol_t device_protocol() const { return PROTOCOL_DEFAULT; };
         virtual void set_callback(i_device_callback * callback) {};
+        virtual void set_derivation_path(const std::string &derivation_path) {};
 
         /* ======================================================================= */
         /*  LOCKER                                                                 */