Add a new file menu option when there are multiple file providers

CURA-7868

resources/qml/Menus/FileMenu.qml

@@ -22,6 +22,11 @@ Menu
     {
         id: openMenu
         action: Cura.Actions.open
+        visible: CuraApplication.fileProviders.length > 0 // DEBUG: It's > 0 so that both options are visible for debugging purposes
+    }
+
+    OpenFilesMenu {
+        visible: CuraApplication.fileProviders.length > 0 // DEBUG: It's > 0 so that both options are visible for debugging purposes
     }
 
     RecentFilesMenu { }

resources/qml/Menus/OpenFilesMenu.qml

@@ -0,0 +1,45 @@
+// Copyright (c) 2016 Ultimaker B.V.
+// Cura is released under the terms of the LGPLv3 or higher.
+
+import QtQuick 2.2
+import QtQuick.Controls 1.1
+
+import UM 1.6 as UM
+import Cura 1.0 as Cura
+
+import "../Dialogs"
+
+Menu
+{
+    id: menu
+    title: catalog.i18nc("@title:menu menubar:file", "Open File(s)...")
+    iconName: "document-open-recent";
+
+
+    Instantiator
+    {
+        id: fileProviders
+        model: UM.FileProviderModel { }
+        MenuItem
+        {
+            text:
+            {
+                return model.displayText;
+            }
+            onTriggered:
+            {
+                if (model.index == 0)  // The 0th element is the "From Disk" option, which should activate the open local file dialog
+                {
+                    Cura.Actions.open.trigger()
+                }
+                else
+                {
+                    fileProviders.model.trigger(model.name);
+                }
+            }
+            shortcut: model.shortcut
+        }
+        onObjectAdded: menu.insertItem(index, object)
+        onObjectRemoved: menu.removeItem(object)
+    }
+}