Add ability to configure QtCreator always to use external editor.

As a developer that has used vi/vim for many years, the weirdnesses of FakeVim drive me crazy. I suggest that you add a way for users to always use an external editor for text editing, especially when double clicking a file. That way, you could close all the FakeVim bugs by sending users to Real Vim. The only support burden you would then have would be tightness of integration with external editors, and you could get out of the editor business. Most other IDEs that I have used over the years have allowed this, and I don't see what is so special about QtCreator. Thank you for listening.