add drag and drop onto app icon (dock etc.) support for MacOS platform.

common/library_item.cpp

@@ -0,0 +1,12 @@
+
+#include "library_item.h"
+
+LibraryItem &LibraryItem::operator=(const LibraryItem &other)
+{
+    this->name = other.name;
+    this->path = other.path;
+    this->parentId = other.parentId;
+    this->id = other.id;
+
+    return *this;
+}