Windows (un)installers should prompt if Vidalia/Tor/Privoxy already running

Migrated from old trac: "If the user tries to run the Windows bundle or Vidalia-only installers with Vidalia, Tor, or Privoxy already running, the installer will fail to install the new executables with little fuss. Similarly, the uninstallers will fail to remove the executables if they are already in use without notifying the user.

It would be better if the installers and uninstallers displayed a message box notifying them if tor.exe, vidalia.exe, or privoxy.exe are still running. Even better would be an option to kill those processes from within the installer, but I'm guessing NSIS doesn't let us do this very cleanly."