message: Bugfix: Optimizer_VP force instead of velocity.
  It seems this makes near to no difference, but now it is implemented correctly.
diff: @@ -79,7 +79,7 @@ namespace Engine
  // Move the spins
  Vectormath::add_c_a(dt, l_velocity, spins_temp[i]);
  - Vectormath::add_c_a(0.5/m*dt*dt, l_velocity, spins_temp[i]);
  + Vectormath::add_c_a(0.5/m*dt*dt, l_force, spins_temp[i]);
  Vectormath::normalize_vectors(spins_temp[i]);
  // Copy out
  