Refactor operation: extract class to file

I believe it would be (mildly) useful to have a refactor operation that would allow to extract a class from a file (resp. a header/source pair of files) containing several classes to its own file (resp. pair of files).

Suggested workflow:

• User opens refactor menu on a class whose name does not match the file's name
• User selects "extract class to a x.hpp/x.cpp"
• Open a dialog to allow the user to modify the file name(s), to prefix with a path for example (similar to the add class dialog)
• Add the file(s) to the project
• Move declarations and implementations of this class to the corresponding file(s)
• Leave the focus on the new file (header if a source file was created as well)