reinstate the getTorques algorithm

and test it together with rnea
test_crba: remove comment
fix doc typo
fix transform.toMatrix()
add "jac" algorithm

which computes the whole kinematic jacobian

This version is slightly slower than the earlier one, except for the
simple humanoid model.

earlier: branch "add_jac" 3d92ad005258c7fff8787dc04b5a0ff0d60831c7

    Model NBDOF : 35
    jac (without jcalc): 6.70407µs

    Model NBDOF : 3
    jac (without jcalc): 0.06787µs

    Model NBDOF : 7
    jac (without jcalc): 0.2179µs

    Model NBDOF : 31
    jac (without jcalc): 2.12443µs

with this commit

    Model NBDOF : 35
    jac (without jcalc): 6.05539µs

    Model NBDOF : 3
    jac (without jcalc): 0.1197µs

    Model NBDOF : 7
    jac (without jcalc): 0.36194µs

    Model NBDOF : 31
    jac (without jcalc): 2.82554µs
backward_traversal: add a 3 args variant
backward_traversal_prev: improve doc
reinstate deepest_common_ancestor algorithm
spatial/transform: fix ambiguous overload
spatial/transform: add missing specializations

and remove unecessary initializations
reinstate jac_point_{relative,robot} algorithms

The algorithm is slightly faster than the first implementation, probably
due to the S matrix improvements.

earlier implementation: commit de8eeafacd60161d9d6aa0cffdeea6b85772b381

    Model NBDOF : 35
    jac_point_robot (without bcalc): 11.0191µs
    Model NBDOF : 3
    jac_point_robot (without bcalc): 0.13529µs
    Model NBDOF : 7
    jac_point_robot (without bcalc): 0.55068µs
    Model NBDOF : 31
    jac_point_robot (without bcalc): 7.00043µs

this commit

    Model NBDOF : 35
    jac_point_robot (without bcalc): 9.96257µs
    Model NBDOF : 3
    jac_point_robot (without bcalc): 0.12361µs
    Model NBDOF : 7
    jac_point_robot (without bcalc): 0.45006µs
    Model NBDOF : 31
    jac_point_robot (without bcalc): 5.3992µs
reinstate jac_point_chain