Add an initial implementation of the sidebar

This still needs design love, and none of the current widgets should be
considered finalized, but it shows the basic ideas.

http://bugzilla.gnome.org/show_bug.cgi?id=581774

js/ui/Makefile.am

@@ -14,6 +14,9 @@ dist_jsui_DATA =		\
 	overlay.js		\
 	panel.js		\
 	runDialog.js		\
+	sidebar.js		\
 	tweener.js		\
+	widget.js		\
+	widgetBox.js		\
 	windowManager.js	\
 	workspaces.js