[README] document ROS_PACKAGE_PATH use

[CMake] pinocchio required only for tests, fix #22

Fix package paths in URDFs - resolve issues 9,19

* Added quadcopter Iris from 3DRobotics

* [readme] add hector and iris to the launch command

* [iris] Added reduced version of the STL file

Co-authored-by: PepMS <jmarti@iri.upc.edu>

delete duplicate file

See merge request !32

robots/talos_data/urdf/talos_reduced.urdf is also available at
robots/talos_data/robots/talos_reduced.urdf

Thanks @nmansard for the repport.

[reduced] Added effort limits for reduced models

See merge request !31

fix __main__

See merge request !30

Migrate universal robot srdf files from hpp-universal-robots.