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/designer/qtcreatorintegration.cpp

@@ -297,7 +297,7 @@ static void addDeclaration(const Snapshot &snapshot,
     declaration += QLatin1String(";\n");
 
     CppTools::CppRefactoringChanges refactoring(snapshot);
-    CppTools::InsertionPointLocator find(&refactoring);
+    CppTools::InsertionPointLocator find(refactoring);
     const CppTools::InsertionLocation loc = find.methodDeclarationInClass(
                 fileName, cl, CppTools::InsertionPointLocator::PrivateSlot);