[paypal] Fix paypal once & for all
This fixes some new python3 issues (
TypeError: a bytes-like object is required, not 'str') in
browser.py, I am not sure why I did not have the issue the other day.
But mainly there were still some cases (paypal does not always send the same obfuscated code) where the scraper failed.
I simplified the code quite a bit and avoided the whole challenge decoder by mimicking the XHR request that the paypal code uses to send the tokens to its verifychallenge URL: instead of actually sending the request I retrieve the values from here and let the paypal code do most of the work.