Support for XDG Base Directory spec. (aka stop filling my ~ up)

[frebib]

https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html

We should be trying for $XDG_CONFIG_HOME/cloudflared first instead of ~/.cloudflared etc. This is a pretty well accepted standard by now. Please consider revising how the directories are structured

[lhanson]

https://github.com/OpenPeeDeeP/xdg makes it dead simple to respect users' preferences, please don't create arbitrary directories in my $HOME.

[furiousteabag]

+1 is it solved?

[mintyfrankie]

+1 Would really love to see this happen -- .cloudflared is for now the only directory that I have to deal with before having a clean home directory.