+ Efficiency improvements:
| avoid transforming clouds already in map frame (added additional
parameter to specify sensor frame_id for calculating sensor pose)
| create occupancy cloud directly as ros message instead of pcl cloud
(avoids conversion)

+ Projection of nav_msgs::OccupancyGrid with customizable height and
initialization as free or unknown.

+ Increased tf listener buffer to 30 sec.

of sensor frame id.

- Line 310 of OctomapServer.cpp was doing an unnecessary internal copy
(pc_nonground = pc), that can be avoided by using shared pointers.
- Improved assembly of pointcloud from octree by using vector reserve
instead of resize.
- Improved parametrization of sensor frame id. This way the input cloud
can be sent in any frame id (map, sensor, other), and the parameter
sensor_frame_id can be used to specify which is the sensor frame to
compute the origin for the raytracing algorithms (used to integrate the
pointcloud into the octree).

reconfigure.

and regulate how often the 2D projection map is published.

messages.