EEG/CSP/BCI example

Issue #1232
The example uses data from here: http://www.physionet.org/physiobank/database/eegmmidb/
A crude downloader is included, but implementing a proper one could be a project for the coding sprint?

I don't know how to get MNE topomaps to work, so I simply used scot/eegtopo for now.

Some experimental or redundant parts of the code were left as comments for now.
these data set does not contain filter information, so the corresponding fields in raw.info are empty.