ui: qt high dpi scaling

* Enabled automatic scaling for high dpi systems that has been introduced with qt 5.6. This is only a temporary solution. We should change the ui code to use only em scales instead of pixels.

src/app/main.cpp

@@ -35,6 +35,7 @@ void init()
 int main(int argc, char *argv[])
 {
 	QApplication::setApplicationName("Coati");
+	QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling, true);
 
 	Version version = Version::fromString(GIT_VERSION_NUMBER);
 	QApplication::setApplicationVersion(version.toDisplayString().c_str());