Add ecs ComponentListener

- Add ecs ComponentListener which listens to Component addition and
  removal
- Add RefCounter class used to keep track of moves and copies

CopiumEngine/src/copium/asset/AssetRef.cpp

@@ -5,51 +5,17 @@
 namespace Copium
 {
   AssetRef::AssetRef(AssetHandle handle)
-    : handle{handle}, refCounter{new int{1}}
+    : handle{handle}
   {}
 
   AssetRef::~AssetRef()
   {
-    if (refCounter == nullptr)
-      return;
-
-    (*refCounter)--;
-    if (*refCounter == 0) 
+    if (refCounter.LastRef())
     {
       AssetManager::UnloadAsset(handle);
-      delete refCounter;
     }
   }
 
-  AssetRef::AssetRef(const AssetRef& other)
-    : handle{other.handle}, refCounter{other.refCounter}
-  {
-    (*refCounter)++;
-  }
-
-  AssetRef::AssetRef(AssetRef&& other)
-    : handle{other.handle}, refCounter{other.refCounter}
-  {
-    other.refCounter = nullptr;
-  }
-
-  AssetRef& AssetRef::operator=(const AssetRef& rhs)
-  {
-    handle = rhs.handle;
-    refCounter = rhs.refCounter;
-
-    (*refCounter)++;
-    return *this;
-  }
-
-  AssetRef& AssetRef::operator=(AssetRef&& rhs)
-  {
-    handle = rhs.handle;
-    refCounter = rhs.refCounter;
-    rhs.refCounter = nullptr;
-    return *this;
-  }
-
   AssetRef::operator AssetHandle() const
   {
     return handle;