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/pythoneditor/pythoneditor.cpp

@@ -50,6 +50,7 @@ namespace Internal {
 PythonEditor::PythonEditor(EditorWidget *editorWidget)
     :BaseTextEditor(editorWidget)
 {
+    setId(Constants::C_PYTHONEDITOR_ID);
     setContext(Core::Context(Constants::C_PYTHONEDITOR_ID,
                              TextEditor::Constants::C_TEXTEDITOR));
 }
@@ -65,14 +66,6 @@ Core::IEditor *PythonEditor::duplicate()
     return widget->editor();
 }
 
-/**
- * @returns Unique editor class identifier, that is Constants::C_PYTHONEDITOR_ID
- */
-Core::Id PythonEditor::id() const
-{
-    return Core::Id(Constants::C_PYTHONEDITOR_ID);
-}
-
 bool PythonEditor::open(QString *errorString,
                         const QString &fileName,
                         const QString &realFileName)