Add Support for XDG Base Directory

[KrishnaSSH]

Please update AO to respect and implement the XDG Base Directory Specification.

Instead of hardcoding paths in the home directory, I looked it up it was storing it's internal files in $HOME/.ao/

the application should dynamically look for standard XDG environment, falling back to the standard defaults if they are not set.

why do this?
it doesn't clutter up user's $HOME directory with hidden dotfiles instead everything can be stored per app wise in $XDG_CONFIG_DIR
it's easier to backup and can be configured to share share with multiple users on a machine.

learn more about this: https://specifications.freedesktop.org/basedir/latest/
how mozilla fixed it: https://bugzilla.mozilla.org/show_bug.cgi?id=259356