Commodity searching on shop form is case insensitive now.

closes #283

shop/shopform.cpp

@@ -392,6 +392,7 @@ void ShopForm::on_commoditySearch_textChanged(const QString &text)
     QSortFilterProxyModel proxy;
     proxy.setSourceModel(m_commodityModel);
     proxy.setFilterKeyColumn(0);
+    proxy.setFilterCaseSensitivity(Qt::CaseInsensitive);
     proxy.setFilterFixedString(text);
 
     auto moveToIndex = [this](const QModelIndex &matchingIndex) {