Allow build and run configurations to be parsed from a file for import projects.

I use waf as my build system, having to manually set the build and run configuration in the editor for an import project (.creator) is something I'd rather have the build system do automatically.
I ran into this issue a long time ago when using Qt Creator with Unreal Engine too.
Having something that Qt Creator parses, and thus a build system can generate should allow for easier adoption/integration of Qt Creator as IDE for unsupported build systems.