[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==

Fix doc of jacobinCenterOfMass