[C++][Geom parser] Removed boolean root_joint_added while parsing. Geom parser modified consequently to look for parent of link in pinocchio model  now instead of urdf::tree parent joint.

[C++][Python][Parser Geom] Parse automatically the ROS_PACKAGE_PATH environment variable if not clue is given by the user to where to search for meshes. Change the meshRootDir argument to a vector of strings (package directories). Updated Python consequently

[benchmark][cmake] Re added boost component. Needed by timings-geometry.cpp, and use correct name of algorithms

By default, one can now build the benchmarks from make timings. They
are build along with the lib if BUILD_BENCHMARK is set to ON.

Added missing licenses, corrected compilation bug in python/parsers.hpp. also modified the number of benchmarks to have more relevant results and removed useless lines

[bench][unittest] Reworked the comparison test between pinocchio and hpp : more tests for benchmarks along with functional tests ; removing magic paths to urdf models + modification of romeo urdf model. Also added a specific BUILD_TESTS_WITH_HPP cmake variable. If you want to run tests that execute hpp robot loading, be sure to have the package romeo_pinocchio installed (it is just a package done done by hand for the moment)

[C++] computeDistances and computeCollisions moved out of GeometryData. Added a vector of boolean handling the state of whether or not the pairs are in collision in GeometryData

[C++][algo] algorithm updateCollisionGeometry now optionally executes algorithm geometry to compute positions before updating collision objects's positions

[C++][Geom] distances results for computeDistances is not always cleared but replaced by a vector with empty results. The initialization of collision pairs is now  always done in constructor.

[benchmark] Added benchmark of atomic computations with geometry objects such as updating global positions, determine if two objects are in collision, or compute the distance between two objects

[Major][C++][Python]Breaking retrocompatibilty. Added the possibility to choose root joint when creating a model (in C++) or a robot (in Python). May be a check can be done on the value of root parameter in python if it's not None

[cmake][C++][bug fix] Moved initialization of static const variable gravity 981 from model.hpp to model.cpp. libpinocchio.so is no more empty. Caution : Pinocchio is more a header-only library. One should alwais link against shared library

Conflicts:

	benchmark/timings.cpp

Scores:
RNEA = 		4.5206 us
CRBA = 		5.29557 us
Cholesky = 	2.33944us
Jacobian = 	3.6358 us
COM+Jcom = 	3.95835 us