ENH MneExperiment:  manage bad channels with files
ENH FileTree:  add cache handlers
ENH TreeModel:  add ._temporary_state context
ENH MneExperiment:  use caching for `evoked-file` and `cov-file`
ENH MneExperiment:  `event-file`

- `raw-evt-file` -> `event-file`;
- cache depending on `raw-file` mtime
ENH MneExperiment:  use caching for `fwd-file`
RF MneExperiment.make_src():  use mne 0.8
ENH MneExperiment.set_root():  use os.path.normpath()
DOC MneExperiment
WIP GUI
WIP:  API:  enforce Dataset keys to valid variable names
WIP naming:  make auto-generated names valid

Var and Effect done
what about “{name}”?
Require mne-python 0.8