"Patching" the V3 IdP in windows.

[Rod Widdowson]

> It would be good to get some experience with this approach [Allow same 
> version installs] and then we can
> maybe apply that to the SP in the future.

I played around with this this morning.  Based on my results I'd be happy
shipping the IdP installer like this.

- Reinstalling with the _same_ installed brings up the
"change/remove/reinstall" dialog.
- Reinstalling with a different installer but the same Version.Sub.SubSub
just works like any other upgrade
- But you still get a sensible warning if trying to downgrade an
installation.

Let's see how this works for a few releases and then add it to the SP...