add activate function properly

While the previous function technically worked, the connections
weren't setup properly. Also the row_count function wasn't running
because it requires a QModelIndex parameter. Added a simple count
function to make sure we know how many slides there are in QML.

src/qml/presenter/Presentation.qml

@@ -365,6 +365,7 @@ FocusScope {
     function nextSlideAction() {
         keyHandler.forceActiveFocus();
         console.log(currentServiceItem);
+        console.log(totalSlides);
         const nextSlideIdx = currentSlide + 1;
         if (nextSlideIdx > totalSlides || nextSlideIdx < 0)
             return;