(poweriso) Correcting 64bit Download Url

- Not sure why I didn't pick up on this earlier, but during moderation,
it was pointed out that there should be a 64bit download URL for
PowerIso
- This has been added in
(poweriso) Made uninstall work on both architectures

- Added a check to see if uninstall is happening on a 64bit machine
- If it is, change the registry key that is used for uninstallation