schema: add reference coordinate system to Poses

[DavidTorresOcana]

Currently, Poses are used to represent SE3 Transformations. A transformation is an affine transformation between two coordinate systems (CS) and, and as such, is bounded to these two (source and destination) coordinate systems.

In other words, a Pose shall indicate the two coordinate system it transforms points in between of.

As, in DGP, each Pose is linked to a datum, a sensor or a piece of information, the only missing CS is the reference (destination) coordinate system.

This PR proposes explicit indication of such Reference Coordinate System on each Pose.

This is in line with ASAM OpenLABEL CS definitions where each piece of information is linked to a CS.

Pending still TODO, but not in the scope of this PR (conversation is encouraged), is how to define and name these CS. ASAM OpenLABEL CS definitions, ISO 8855 and ISO 23150 are a good start.

@rachel-lien @akira-wakatsuki-woven ping

This change is 

[DavidTorresOcana]

dgp/utils/pose.py line 171 at r2 (raw file):

Previously, rachel-lien wrote…

nit, can you update the docstring parameters section for ` reference_coordinate_system` per style guide? https://github.com/TRI-ML/dgp/blob/master/docs/CONTRIBUTING.md#code-style https://numpydoc.readthedocs.io/en/latest/format.html#parameters

It seems I missed to document these. New commit should address these

[DavidTorresOcana]

dgp/utils/pose.py line 92 at r3 (raw file):

Previously, yuta-tsuzuki-woven wrote…

nit, I think you need to add `Parameters` explanation in the docstring ``` Parameters ---------- new_reference_coordinate_system: str ... ```

oh! I missed this! Thank you for catching it. I also updated the docstring style of that file to match Numpy's

[DavidTorresOcana]

is it ok to merge?

[DavidTorresOcana]

Anything else to do @rachel-lien @yuta-tsuzuki-woven ?