switch to pyaes for password decoding

[gfrlv]

Description

removed the Cryptography dependency in favor of pyaes. Cryptography was used in only one place: to decrypt the mylogin.cnf file.

This is a first step towards #950: Cryptography is a pain to package because it relies on a lot of data files. It can be done, but either there will be a large useless memory footprint (those files need to be loaded into ram), or it will require a lot of hacking into the guts of Cryptography to get rid of the parts we don't need. I don't think it's worth the effort.

Checklist

• [x] I've added this contribution to the changelog.md.
• [x] I've added my name to the AUTHORS file (or it's already there).

[gfrlv]

pyaes is, of course, less audited than Cryptography, if we needed it for something serious there would have been security issues to consider, but encryption of that mylogin.cnf file is a joke anyway, we can just take whatever works.