[MSVC] Copy build output to src/ automatically after build

I got frustrated many time that I run functional tests on an outdated binary.

This make sure that files are properly copied (and debuggable) for functional tests after a build.

This PR add a common.vcxproj which can be used to extend the build steps. I can't move it in common.init, because build step customization must always come at the end of a project file.