lookingGlass: Get font from GConf

Instead of using "Monospace", pick the users configured monospace font
name up from GConf. (This is a nice touch, but is more done here to
demonstrate that we can do it rather than for any great utility.)

https://bugzilla.gnome.org/show_bug.cgi?id=591245

data/theme/gnome-shell.css

@@ -70,7 +70,6 @@ StScrollBar StButton#vhandle:hover
   padding: 4px;
   border: 1px solid rgba(0,0,172,0.85);
   border-radius: 4px;
-  font-family: Monospace;
 
   color: #88ff66;
 }