Refactoring changes: Cleanup and improvements.

Previously RefactoringFiles were usually passed around by value.
However, since a RefactoringFile may sometimes own a QTextDocument
(when it was read from a file), that's not great and caused the
file to be reread after every copy.

With this change RefactoringFile becomes noncopyable and is always
owned by a shared pointer.

This change also allowed having const RefactoringFiles which is
useful because they can be safely used from other threads. See
CppRefactoringChanges::fileNoEditor.

Change-Id: I9045921d6d0f6349f9558ff2a3d8317ea172193b
Reviewed-on: http://codereview.qt.nokia.com/3084
Reviewed-by: Leandro T. C. Melo <leandro.melo@nokia.com>

src/plugins/texteditor/basetexteditor.cpp

@@ -169,7 +169,7 @@ Core::IEditor *BaseTextEditorWidget::openEditorAt(const QString &fileName, int l
     Core::IEditor *editor = editorManager->openEditor(fileName, editorKind,
             flags, newEditor);
     TextEditor::ITextEditor *texteditor = qobject_cast<TextEditor::ITextEditor *>(editor);
-    if (texteditor) {
+    if (texteditor && line != -1) {
         texteditor->gotoLine(line, column);
         return texteditor;
     }