qt: fix platform specific file dialog filters

Translations now only contain translation for the description and
extensions are generated in code taking account platform specific
differences.

src/qt/qt_util.hpp

@@ -0,0 +1,14 @@
+#ifndef QT_UTIL_HPP
+#define QT_UTIL_HPP
+
+#include <QString>
+
+#include <initializer_list>
+
+namespace util
+{
+    /* Creates extension list for qt filedialog */
+    QString DlgFilter(std::initializer_list<QString> extensions, bool last = false);
+};
+
+#endif