Implemented a load of Z80 OpCodes. Added SimpleIOBus.

Core/Memory/MemoryBus.cs

@@ -24,15 +24,14 @@ namespace Core.Memory
 
             if (address < 0x4000)
             {
-                // Attempted to write to the ROM area. 
-                // We simply ignore the write command, just like real hardware.
+                // Cannot write to ROM - Do nothing - maybe throw an exception
                 return;
             }
 
             _memory[address] = value;
         }
 
-        // Helper method to load the original Sinclair ROM file
+        // Load the ROM file
         public void LoadRom(byte[] romData)
         {
             if (romData.Length > 0x4000)
@@ -40,7 +39,7 @@ namespace Core.Memory
                 throw new ArgumentException("ROM file exceeds the 16KB capacity of Bank 0.");
             }
 
-            // Copy the ROM data into the very beginning of the memory array
+            // Copy the ROM
             Array.Copy(romData, 0, _memory, 0, romData.Length);
         }
     }