Add Scene with systems

- Add Scene class which populates the engine with Systems which handles
  all logic in the game
- Add Systems to ecs

CopiumEngine/src/copium/asset/AssetRef.cpp

@@ -0,0 +1,58 @@
+#include "copium/asset/AssetRef.h"
+
+#include "copium/asset/AssetManager.h"
+
+namespace Copium
+{
+  AssetRef::AssetRef(AssetHandle handle)
+    : handle{handle}, refCounter{new int{1}}
+  {}
+
+  AssetRef::~AssetRef()
+  {
+    if (refCounter == nullptr)
+      return;
+
+    (*refCounter)--;
+    if (*refCounter == 0) 
+    {
+      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;
+
+  }
+}