QmlProfilerTraceClient: Cleanup

Move private members into d pointer, remove unused signal,
rename clearView() method & clear() signal to clearData(), dataCleared()

Change-Id: I0baf78107861a469185c736fc448b4d3a7929cdd
Reviewed-on: http://codereview.qt.nokia.com/2691
Reviewed-by: Kai Koehne <kai.koehne@nokia.com>

src/plugins/qmlprofiler/qml/MainView.qml

@@ -163,7 +163,7 @@ Rectangle {
             }
         }
 
-        onClear: {
+        onDataCleared: {
             root.clearAll();
         }