ENH Dataset.aggregate():  ADD equal_count argument
API Factor:  cells in tuple instead of list, LazyProperty
FIX Celltable:  numerical `X` and `cat`
ENH t_contrast:  allow cells with "*"
ENH TreeModel:  compounds

automatically update compounds composed of different elements, skipping
elements that are = ""
ENH MneExperiment:  `sns-kind` compound
ENH MneExperiment:  `evoked-kind` compound
ENH MneExperiment:  ADD option to equalize trial count in evoked files
FIX MneExperiment.load_events():  `edf` kwarg
FIX MneExperiment:  delete mne Raw from evoked-files