Investigate formats for storing taxels poses within local robot frames

[xEnVrE]

As per https://github.com/icub-tech-iit/tickets/issues/2728, we need to identify - and make tests to assess feasibility - candidate formats to store positional data which identify the pose of taxels within the skin patches.

Thus far, we considered as possible options:

• a twin URDF of the robot with skin data only;
• the standard URDF of the robot augmented with skin data;
• the standard UDRF of the robot with an additional file containing skin data.

Tools worth mentioning are

• SRDF
• xacro