Core: Make IEditor::id a value member and adjust users

Change-Id: I47e457c4a1821c515cd8a740d27bfe005a0c09e6
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/imageviewer/imageviewer.cpp

@@ -62,6 +62,8 @@ ImageViewer::ImageViewer(QWidget *parent)
     : IEditor(parent),
     d(new ImageViewerPrivate)
 {
+    setId(Constants::IMAGEVIEWER_ID);
+
     d->file = new ImageViewerFile(this);
     d->imageView = new ImageView();
 
@@ -137,11 +139,6 @@ Core::IDocument *ImageViewer::document()
     return d->file;
 }
 
-Core::Id ImageViewer::id() const
-{
-    return Core::Id(Constants::IMAGEVIEWER_ID);
-}
-
 QWidget *ImageViewer::toolBar()
 {
     return d->toolbar;