Thanks for this PR!

I understand better what you want to do now 😼 I had also worked on something similar to limit the CoM acceleration for our humanoid robot. As we are interested in making Tasks better, I would rather like to have a generic bounds constraint, that will allow to share the adding/removing/updating mechanics at least.

In the very end, I'd like all the "bounds" constraint to share most of the computing logic. Ideally, they should only differ by the dimension and the way we compute the Jacobian.

Additionally, it would be nice if it would be generic for directions i.e. instead of enforcing:

l  <= J qdd + Jd qd <= u

Enforcing for every direction n:

l <= (J qdd + Jd qd).dot(n) <= u

I will maybe see with @gergondet and @aescande if it's better to accept this PR as is or wait for some refactoring.