skiller: add support for finalization callbacks

Maintain a list of callbacks for finalization that is called just before
the Lua context is shutdown.
skiller: pass ROS node name and no_print_funcs parameter
skiller: setup roslua logging to be piped through Fawkes

Replace roslua's default logger with one that outputs to the Fawkes
logger. This eases the integration of roslua-based code into the Fawkes
skiller with ROS integration.
Merge remote-tracking branch 'origin/timn/skiller-ros' into dfg-demo-2014