ENH MneExperiment.show_subjects():  add count and mri columns
ENH MneExperiment.show_subjects():  use current group instead of parameter; add caption
ENH Experiment.show_state():  add `hide` parameter
FIX MneExperiment:  stc_ndvar call
API MneExperiment.add_epoch_stc()

- add option for source space baseline correction
- make etc NDVar name consistent between evoked and epochs
API MneExperiment:  .add_evoked_label() —> .add_stc_label(), handle epochs as well as evoked datasets
ENH MneExperiment.add_evoked_stc():  when morph is requested and all subjects are common_brain, don’t morph
ENH MneExperiment:  add epoch parameter `sub`
FIX MneExperiment.iter():  only include subjects in the current `group`
ENH MneExperiment:  make _derived_labels an attribute
ENH MneExperiment:  _process_subject_arg() to unify combined group/subject argument
ENH MneExperiment.show_subjects():  return Dataset
ENH MneExperiment:  gather ._values from all base classes
RM MneExperiment:  ttests and rm_fake_mris()
ENH MneExperiment:  results file structure
ENH MneExperiment:  ADD ttest movies
ENH MneExperiment:  add `._model_order = []` attribute to specify order of factors in models
ENH MneExperiment:  epoch event selection

Select events for epochs based on expression rather than than `stimvar` and `stim`
ENH MneExperiment:  simplify epoch description

 - only use `epoch` and `rej` in templates
 - move `pad` into epoch specification dict
 - rename epoch selection and evoked dirs
ENH Experiment state management

store_state() an restore_state() methods