ENH MneExperiment:  ADD .make_test() and test-file
FIX fmtxt List:  handle subordinate lists; DOC
FIX is_fake_mri():  don't expect "label" directory
ENH MneExperiment.show_subjects():  return type through argument

return as fmtxt.Table or Dataset
ENH plot.brain:  image() function to create FMTxt image from Brain
ENH MneExperiment:  ADD .make_report_clusters()