Added a new SensorMap variable to store all sensors.
More integration with the SensorMap.

SensorMap is correctly deleted on class destruction.
Laser orientation and angle increment are independent and are
stored within the RangeSensor class (two new arguments on the
constructor).
Variables gsp_laser_ and gsp_laser_angle_increment_ have been
removed.
Array of laser angles now initiated on sensor constructor.
Particles are now published on its own thread.

New flag to know if the GridSlamProcessor is initialized.