tests: fix tests to run without x server

src/tests/TestImport.cpp

@@ -1,6 +1,6 @@
 #include <QTemporaryFile>
 #include <QtTest/QTest>
-#include <QApplication>
+#include <QCoreApplication>
 #include <QTextStream>
 
 #include "csvparser.h"

src/tests/TestImport.h

@@ -13,7 +13,7 @@ public:
     ~TestImport();
 
 private:
-    QApplication* app;
+    QCoreApplication* app;
 
 private slots:
     void csvImport();