Extend the schemas of the property definitions with missing fields (notably, all those of the trajectory endpoint)

[giovannipizzi]

As soon as #377 is merged, we need to update the property definitions to also include all those of the Trajectory endpoint.

• Add all those of structure, but define only the outer layer with a new first dimension of name dim_frames. Remember to set compactable to a list with the first value constant and all other values no (with appropriate length). Link the subfields to existing definitions for the structure properties.
• add also the nframes and reference_frames definition.