cmake: add a dependency on config and license files
simple-arm: remove prefer-fixed-axis option

in orther to provide some testing for the RevoluteAxisAny joint.
(note: we should really do unit tests)
fix ConstraintMotionAnyAxis init

this fixes the simple-arm crba test
some ConstraintMotion* cleaning
Merge branch 'fix_init_reborn_again'
robotbuilder: remove Xt and sXp types from model

since they are not used anymore
robotbuilder: remove mass from the model

because it is not used and is available in the Spatial::Inertia
anyway.
robot builder: more input validation
robotbuilder: remove replacements_ member
robotbuilder: remove unnecessary is_initialized checks
robotbuilder: check name & libname
robotbuilder: remove unused member variable
reinstate the getTorques algorithm

and test it together with rnea
Merge remote-tracking branch 'laas/master' into qibuild
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