Split the tutorial.rst file in several components.

[papadop]

In case it is not in conflict with other changes... Otherwise, I can redo it....
Still not completely convinced by the rst format but since this is the most up-to-date tutorial let's put it in shape.

[agramfort]

this is just splitting files? no edits?

[agramfort]

just use:

.. contents:: Table of Contents
   :local:
   :depth: 2

.. include:: Data.rst
.. include:: Commands.rst
.. include:: Examples.rst
.. include:: Appendix.rst

and you have your include and you can split the files in subfiles. I tried it works.