Smooth changings for sot-core

The right one is feature-posture.hh

The exception thrown did not have the good type.
As a result, printing for example
robot.featureComDes
would crash.

Remove explicit dependency on gfortran

Before this commit, it was impossible to build the project in-place
(without a separate build directory) as the traces directory and
traces test were conflicting in unitTesting.

[skip ci]

  Add a command to switch from first to second order kinematics.
  In second order kinematics, configuration second derivative is equal to
  control.
  velocity is provided as output signal.