add confirmation screens

[zweilous]

without confirmation screens, it's pretty easy to accidentally overwrite/delete a backup or write to a slot. the confirmation screen for each function should be specific in saying what it's about to do because memorizing the button mapping isn't intuitive for something that isn't used constantly and pressing select to see the instructions as a reminder is just an extra press.

and speaking of which, the instructions can fit on the bottom of the top screen instead of having all that negative space there. makes having to press select unnecessary.

thanks for this tool!