This new method give the increment for finite difference applications.

There are still some bugs inside differentiate, interpolate

Most of the joints have bugs inside their methods - integration,
differentiate, interpolate.
A small remind that the joint velocity vector is generally expressed in
the joint frame while the translations are expressed in the joint
parent frame.

Minor rework of joint class

It replaces the old shortname  method with is no more static

[C++] The cloud of points in GeometryObject is now a fcl::CollisionGe…

[C++] The cloud of points in GeometryObject is now a fcl::CollisionGeometry instead of fcl::CollisionObject

[CMake] urdfdom is optional

[Minor] avoid re-placing world geoms.

Topic/radius unittest

se3::computeDistances return the index of the shortest distance.

Conflicts:

	unittest/geom.cpp

Conflicts:

	unittest/geom.cpp

Topic/model refactoring

CollisionPair does not invert indexes. Add CollisionPair::operator==