Add option parser using boost::program_options

Now it's possible to set options using the command line or a
configuration file. If the same option is set in both command line and
config file the cmd line option will be prefered.

For now only the following options are available:
  --help
  --version
  --replay
  --data-path
  --log-file
but others should be added as needed.

NOTE: technically there will be no distinction between program options
and parameters, but parameters will be prefered to be set in a
configuration file since they change less often than program options.
Set timing infos for the camera.

Aparently that was the reason the sensor manager was not being able to
select the "best_candidate". I still don't really understand what's
going on inside sensor manager though.

Thanks to Cyrille Berger for investigating this.
Small fixes. Not a big deal
Add tf broadcaster of estimated robot pose

The broadcast needs to be a pointer because if not it wil try to
initialize the node handler before the ros::init, leading to a runtime
crash.

The parent frame is set to "world" since "uav0/origin" didn't work
(don't know why yet). It's not a problem because they are in the same place.

NOTE: "using namespace boost" was removed because it was causing an
ambiguity between our signal function and boost::signal (added from
tf/transform_broadcaster.h)