New flexyble payloads for DT ttrig, vdrift and uncertainties

New payload format for DT ttrig, vdrift and uncertainties, to allow for additional flexibility, e.g. introduce dependencies from track angle, position in the chamber etc. Some of these dependencies are hardcoded corrections in the code at the moment, or cannot be implemented at all.

This PR just includes payload definition, records, and tools to read/write the new format. It includes no change in the existing format, nor any usage of the new format in reconstruction code.