as per UX

(based on gnome-shell/maynard)

We switch to a private shell protocol from here on.  This might get
folded back into weston's desktop shell protocol at a later point when
we see what else is needed.

so we can style lockscreen, panel and favorites

so we can set it form settings later on

Make this a native package so we don't have to worry about patches,
tarballes, etc.