Improve error message and documentation for mainstream use-case

[amynbe]

It took me a while to understand how to correctly use this app.
Most people will likely want to use Wii U Account Swap to transfer their Wii U user from Nintendo to Pretendo.
Which means they merely need the ability to unlink their Nintendo account from their user, and then do the rest from the Wii U menu, i.e. link a Pretendo account to their Wii U user.

A few problems currently with the documentation and application UI:

• There should be a how-to in the main readme on the main use-case above.
• The main readme currently starts with "A tool to manage a user's account.dat". That's both too low-level and too broad. It should say something like "A tool to unlink, relink and back up your Nintendo/Pretendo accounts associated with your Wii U user"
• The error message Have you made a backup for this user and account? is misleading because 1/ it can be understood as a "too late" error message, as in "this error is bad, i hope you had made a backup of your account before hand" while it actually means the operation can't proceed because of a missing account.dat (and I only understood this by looking at the code). 2/ It's likely not the instruction that the user needs. They need to be told instead "Pretendo account.dat not found. First link a Pretendo account to this user via the Wii U user menu, then make a backup of it via this app"
• The error message "the account.dat does not match the current user" could be improved to also say "don't move an account.dat file from another user manually, instead, link your Pretendo account to this user via the Wii U menu"

On a separate note, I think the main use case of unlinking the Nintendo account to make room for a Pretendo account should be a functionality available in Inkay, or at the very list the Pretendo doc and/or Inkay app should clearly tell people how to do so via Wii U Account Swap. This would lower the bar for more people to join the Pretendo community. People trying to joining Pretendo should be invited to unlink their Nintendo account first, so they don't uselessly create an extra Wii U user.

[Nightkingale]

Hi there, apologies for the late response. I agree that the documentation is lacking. I have all kinds of information split up in various places at the moment, but nowhere concrete that the user would easily find (either in the README or in-app would be amazing).

I have always planned to sit down at some point and add a how-to to the README, I just haven't had the time to over the last few months. I also agree that a lot of the error messages could be worded a bit better, and I'd also like to sit down and work on this eventually.

If somebody wants to beat me to any of this, I would love to merge pull requests that address these areas. Otherwise, I will work on this as I have time. Thank you!