Allow the user to use all tags read by cmus (cmus-remote -Q|grep ^tag)
as part of the displayed data (plus the special 'tags' "duration" and
"position").
Add a new module "disk" that takes an optional parameter (the path) and
displays free & total disk space, along with the usage percentage.
Also, added Tunnel/VPN support to the themeing of the "net" module.