added Articulated soft robot loader and description (#115)

* added Articulated soft robot loader and description

* removed the unneccesary files and the deprecated loader function

* added license and readme

* renamed the readme file and added these files in twodof robot description

* remove use less file

* remove useless file

* Update test_load.py

* removed useless folder and plugins from the urdf

Co-authored-by: Justin Carpentier <justin.carpentier@inria.fr>