Added serial command ids; id-to-folder mapping now works.

include/controller.h

@@ -24,6 +24,7 @@ private:
 	String _serial_buffer = String();
 	void _execute_serial_command(String cmd);
 	void _execute_command_ls(String path);
+	void _execute_command_ids();
 	void _execute_command_help();
 	unsigned long _button_last_pressed_at[NUM_BUTTONS];
 	bool _check_button(uint8_t btn);