Improvements for the Read N26 node

[camyyssa]

1. Show message that you need to confirm the login

The first time the node is run, you need to confirm your login in the app. While the app is waiting I think we should show a message: Confirm your login on your N26-paired device

It's pretty hard to figure out what's going on if you don't already expect it. Even I tend to forget about it, and I use the script for all my budgeting.

2. When you approve the login, you get error:

Unexpected token in JSON at position 0

If you try running the ReadN26 node again, it works. Whatever N26 responds with the first time, is not a JSON and it can't be parsed.