Robots are still in 16.04 LTS

The initialization was using std::numeric_limits<double>::min
instead of std::numeric_limits<double>::lowest.
Add a unit test.
Fix #71

Add missing r2d2.urdf.

[Python] Add convenient function to create a robot from a URDF file.

Olivier Stasse authored 4 years ago and olivier stasse committed 4 years ago

The tests NEED to be updated.

Avoid unnecessary recomputation.