Added preview menu and shortcuts for qt quick (Ctrl+Alt+R)

This was needed since we cannot start stuff otherwise without a project

Task-number: BAUHAUS-450
Reviewed-by: kkoehne

src/plugins/qmljseditor/qmljseditor.h

@@ -215,6 +215,7 @@ public:
 public slots:
     void followSymbolUnderCursor();
     virtual void setFontSettings(const TextEditor::FontSettings &);
+    void openPreview();
 
 private slots:
     void onDocumentUpdated(QmlJS::Document::Ptr doc);