Move IEditor::createNew to IDocument::setContents

The method is for setting the contents, so it belongs to the document,
and should be named correspondingly.

Change-Id: I40363dc08f11268f530885b512e4a88e8b10d096
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/diffeditor/diffeditor.cpp

@@ -67,12 +67,6 @@ DiffEditor::~DiffEditor()
         delete m_widget;
 }
 
-bool DiffEditor::createNew(const QString &contents)
-{
-    Q_UNUSED(contents)
-    return true;
-}
-
 bool DiffEditor::open(QString *errorString, const QString &fileName, const QString &realFileName)
 {
     Q_UNUSED(errorString)