Organizing supervised methods

@kaichogami @dengemann @alexandrebarachant @agramfort @jona-sassenhagen @choldgraf

As you know, the aim of the GSoC is to clean up the decoding module. However, I’m not entirely clear on how to guide @kaichogami in terms of module and objects location.

I think we have two options:

• either we keep the transformers in their ‘natural’ locations e.g. mne.preprocessing.ICA, mne.preprocessing.Xdawn
• or we re-unite all the sklearn transformers and estimators in mne.decoding and mne.encoding (or mne.supervised) module.

Opinions?

[larsoner]

Sounds good to me thanks for taking the time to hash it out

[choldgraf]

Would it be too confusing to have functions live in their current places (e.g., preprocessing etc) but have objects meant for sklearn-style fitting built on top of those functions and living in some kind of learn or supervised module (e.g., with a pointer in their docstring to say where their underlying function lives)?