Request additional information from users

Tagging backends may benefit from receiving user-defined parameters from the web UI.

More importantly, some file formats require additional information so that the data can be properly rendered and analyzed. For example, FIMTrack v2 csv files encode positions in pixels and time steps as frame indices. In this specific case, as a bare minimum we need the actual frame rate. Currently, a rigid 30-fps frame rate is considered per default.

To allow the user to supply such required information, we may consider various solutions at the UI level. However, because the tagging backends also expect this information, it would make more sense to store this information in a metadata/header file along with the original data files. Generally speaking, such information should be stored along with the data, for completeness and increased reproducibility.

Proposal: In the documentation, make a proposal of json-based file format to store metadata in the simplest way. In LarvaTagger.jl, automatically read these files.

This mechanism could similarly apply to tagging backends.

An important question here is: Can we consider global parameters only, and have a single metadata file per data repository and tagging model instance? How to identify such a file if not a siblings of every data files?