Allow list of transformations in a camera calibration.

[rodja]

Currently the extrinsics of a camera callibration only allow a single transformation. That's fine for cameras placed at fix positions in the world. But for cameras mounted somewhere on a mobile robot we need the ability to have a local robot coordinate system and update the position in the world while driving. It could also get even more nested if the mobile robot has an n-DOF robot arm with a camera mounting.

As @NiklasNeugebauer pointed out, we may want to look into adapting https://github.com/dfki-ric/pytransform3d to do such transformations.

[rodja]

Maybe it would be good to merge #98 before implementing this. Or we do this first...

[falkoschindler]

Concept:

• extend Calibration class with extrinsics: list[Pose3d] = []
• remove rotation from Intrinsics
• thoughts about persistence:
  • volatile poses vs. hardware-specific constants
  • how to load shared references from persistence? (see Improve startup lifecycle and persistence initialization #106)

[falkoschindler]

This feature has been implemented in PR #153.