[ENHANCEMENT] Add the ability to download previous updates.

[ghost]

When selecting an update for a game, you should be able to select which updates to download from a list of checkboxes. I don't think this would be considered bloat, this has many actual use cases. This would also require downloaded update folders to be renamed to include their version number to prevent duplicate folders.

[yamathedestroyer]

As far as I know, NUS for WiiU doesnt store older updates, as newer ones are always compiled in a way to include every update before.

[ghost]

Wii U USB Helper has this functionality, so I assume that the same functionality can be implemented in this program.

[intra0]

I can confirm that I would really like this feature too. its the one reason I still need usb helper

[intra0]

also should be noted this issue is a duplicate of #85