FIX data-objects:

- eval X in dataset.compress()
- remove special case for dataset when mne.Epochs did not have len();
- add `name` argument to combine()
ENH mne_experiment:  inv state; load evoked

- new 'inv' state that contains complete info on inverse operation;
- improvements to load evoked methods
FIX mne_exeriment:  in .get_templates(), copy() original templates dict before modification
FIX mne_experiment:  set subjects_dir in .add_evoked_stc()
FIX? wxterm:  On startup, show dummy modal dialog, which avoids invisible windows
STY wxterm/wxutils:  cleanup
STY mne_experiment
ENH dataset:  add dataset.rename() to rename data-object
ENH mne_experiment:  epoch selection and rejection

- var_values -> field_values
- update to fields `epoch`, `rej`
  - remove `epochs` field, require all epochs to be named, allow `epoch="e1|e2"`
- mark field_values and secondary values in templates
- add {rej} to epoch, make rejection modular
FIX mne_experiment.rename(): expand template;  fix common prefix search
ENH mne_experiment.reset():  exclude root by default
FIX wxterm shell .OnFileOpen():  Stop when unpickling fails
TEST:  include info.keys() in dataset equivalence test
ENH dataset.eval():  raise if expression is not basestring
ENH dataset.compress():  allow X=None to reduce to a single case
ENH dataset.compress():  add drop kwarg