Panel support for bas dir spec

[Jasper Huijsmans]

FYI,

I just committed changes to the panel to support the base dir spec. At 
the same time I renamed the config file. The panel will copy any old 
configuration files in ~/.xfce4/ to the new locations (unless there are 
already files there of course).

~/.xfce4/xfce4rc -> ~/.config/xfce4/panel/contents.xml

/etc/xfce4/xfce4rc -> /etc/xdg/xfce4/panel/contents.xml

~/.xfce4/settings/panel.xml -> ~/.config/xfce4/mcs_settings/panel.xml


Let me know if anything breaks.

	Jasper