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/libs/cplusplus/ASTPath.h

@@ -54,9 +54,9 @@ public:
     {}
 
     QList<AST *> operator()(const QTextCursor &cursor)
-    { return this->operator()(cursor.blockNumber(), cursor.positionInBlock()); }
+    { return this->operator()(cursor.blockNumber() + 1, cursor.positionInBlock() + 1); }
 
-    /// line and column are 0-based!
+    /// line and column are 1-based!
     QList<AST *> operator()(int line, int column);
 
 #ifdef DEBUG_AST_PATH