Windows installer behavior change

By popular demand, Windows installer now adds Rust bin directory to the PATH by default. If that's what you want, you can just hit the [Install] button without going through the "advanced" dialog sequence.

Q: What happens if I install more than one version concurrently?
A: Since rustc directories are appended to the PATH, the first installed version wins. You can still select other versions by launching Rust shells via shortcuts installed in the Start menu.

Note that you can override default installation state of features from the command line. For example, if you'd rather not install documentation or modify path, you can do this: msiexec /i <path to the .msi package> ADDLOCAL=ALL REMOVE=Docs,Path. You can also skip interactive UI alltogether by tacking on /qr or /qb flags. For a completely silent install use /qn.

I like this change! It would lower the barrier for newcomers who mistakenly do not check the PATH option while installation.

One thing though, wouldn't that make a bit more sense to prepend the Rust directory to PATH, to make the last installed version chosen? I presume this behavior would be what typical users want. I can already imagine receiving questions like "installed the new version of Rust, but still the previous one is used". Is there a fundamental limitation that prevents PATH from being prepended?

We can do that, but it smacks too much of "My program is the most important thing on your system" syndrome for my taste.

Is it possible to scan the existing PATH for conflicting executables, and prompt the user for whether they want to prepend or append the new entry?