Implement algorithms and expose quantities in centroidal coordinates

[diegoferigo]

This issue is mainly a collection of desired features in centroidal coordinates:

• Centroidal momentum ${}_G \mathbf{h} \in \mathbb{R}^6$.
• Add a new VelRepr.Centroidal to obtain the centroidal dynamics using the frame $G := ({}^W \mathbf{p}_{\text{CoM}}, , [W])$ as base frame.
• [...]

[diegoferigo]

It would be nice also adding a new VelRepr.Centroidal to obtain the centroidal dynamics using the frame $G := ({}^W \mathbf{p}_{\text{CoM}}, , [W])$ as base frame. However, this change is more intertwined within the whole JaxSim architecture.

xref https://github.com/robotology/idyntree/issues/85

[diegoferigo]

Many quantities related to centroidal dynamics have been implemented in #117.

[diegoferigo]

The last interesting quantity related to the CoM has been implemented in #161. I think that now JaxSim provides the same quantities as iDynTree. This issue can be closed as completed.