Add SVG multi export

Add a second SVG export option that allows for exporting
a series of icons of various size in one go. A dialog is shown
that allows for entering a file name pattern with place holders
and a list of sizes.

Change-Id: Ic644a9d402aa44af5899c29cf83051fdd7bba3d1
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Diana de Sousa <diana.desousa@theqtcompany.com>
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/imageviewer/imageviewerplugin.cpp

@@ -113,6 +113,14 @@ void ImageViewerPlugin::extensionsInitialized()
         if (ImageViewer *iv = currentImageViewer())
             iv->exportImage();
     });
+
+    a = registerNewAction(Constants::ACTION_EXPORT_MULTI_IMAGES, tr("Export Multiple Images"),
+                          QKeySequence());
+    connect(a, &QAction::triggered, this, []() {
+        if (ImageViewer *iv = currentImageViewer())
+            iv->exportMultiImages();
+    });
+
 }
 
 QAction *ImageViewerPlugin::registerNewAction(Core::Id id,