Finished implentation of devices and added Opcode class

ass2/simulator/device.h

@@ -13,14 +13,14 @@ public:
 };
 
 class InputDevice : public Device {
-    istream& input;
+    istream* input;
 public:
     InputDevice(istream& in);
     unsigned char read() override;
 };
 
 class OutputDevice : public Device {
-    ostream& output;
+    ostream* output;
 public:
     OutputDevice(ostream& out);
     void write(unsigned char value) override;