The geometries are now loaded by reading again the URDF file. From now,
one has to build a model first from a URDF file, then to load the
geometries according to this model.

This reference is mandatory, just because a GeometryModel is linked to
a kinematic Model

Handle SRDF file parsing for activation of collision pairs

This new feature allows to activate collision pairs according to an
SRDF file

Enhance documentation + correct bug in Frame + minor modif

There were some bugs in the algo + rename framesForwardKinematic in
framesForwardKinematics (follow the API)

Enhanced geometric parser, Geometry and use of Model::Index

[C++][Geom] GeometryData::collision_results is now a vector or CollisionResult ( struct holding infos about contacts)