[cob_twist_controller] GPM-based solvers - check nullspace dimension

[fmessmer]

e.g. in GPM-solver check whether projector is Null-Matrix, which means pinv * this->jacobian_data_ is Eigen::MatrixXd::Identity which means this->jacobian_data_ is invertable/regular and thus Nullspace is empty thus the projection has not influence on q_dots_out

Add a check for this, print a warning and skip loop over constraints simply setting Eigen::MatrixXd qdots_out = particular_solution

This would help understand why e.g. collisions happen although CA is activated!

Do this for Stack-of-Task and Task-2nd-Prio, too

@fmessmer FYI