Support the freedesktop base directory specification on *nix derived operating systems

Subject: Support the freedesktop base directory specification on *nix derived operating systems

From: Ryan Delaney

Date: Tue, 7 Jan 2020 18:26:46 -0800

Hi,

Currently, megatools looks for ./mega.ini and then ~/.mega.ini

Following the freedesktop basedir spec
<https://www.freedesktop.org/wiki/Specifications/basedir-spec/> I propose
the following precedence instead:

1. ./mega.ini
2. "$XDG_CONFIG_HOME"/megatools/config
3. "$HOME"/.config/megatools/config
4. ~/.mega.ini

By falling back to old behavior in #4, backward compatibility would be
maintained.
--
Regards,
Ryan Delaney
ryan.delaney@gmail.com