Sort insertion order using int instead of string.

Related to #583

src/bin/abstractprojectitem.cpp

@@ -132,7 +132,7 @@ QVariant AbstractProjectItem::getData(DataType type) const
         data = QVariant(m_thumbnail);
         break;
     case DataId:
-        data = QVariant(m_binId);
+        data = QVariant(m_binId.toInt());
         break;
     case DataDuration:
         data = QVariant(m_duration);

src/bin/projectsortproxymodel.cpp

@@ -124,6 +124,9 @@ bool ProjectSortProxyModel::lessThan(const QModelIndex &left, const QModelIndex
         if (leftData.type() == QVariant::DateTime) {
             return leftData.toDateTime() < rightData.toDateTime();
         }
+        if (leftData.type() == QVariant::Int) {
+            return leftData.toInt() < rightData.toInt();
+        }
         return m_collator.compare(leftData.toString(), rightData.toString()) < 0;
     }
     if (sortOrder() == Qt::AscendingOrder) {