Read configuration from ~/.config/conky/conky.conf

Try to load configuration from ~/.config/conky/conky.conf before
falling back to ~/.conkyrc and /etc/conky/conky.conf.

Quite often Conky configuration comprises several files. It seems
quite convenient to put them all in a single directory which follows
the XDG Base Directory Specification.

Conky still reads ~/.conkyrc for backward compatibility.