TODOs & FIXMEs

repro must have foreign keys to dataset and subject
Dataset finding samplerate in stimuli.dat can be improved
Reading fi data from old-style directories
maybe delegate this to Stimulus?
implement alternative dataSources, somehow
stimulus contrast is not read from nix file (e.g. filestimulus) maybe a problem with all mutables?
Add relacs_nix_version to dataset, could be used to decide how to read stuff, in particular, we will switch to DataFrames for most features after nixio version 1.5