support for CoSMoMVPA

CoSMoMVPA is a toolbox in matlab inspired by PyMVPA.

This PR provides
- dataset input/output support
- neighborhood (a.k.a. query engine) input support
- unit tests
I really doubt that out doctests would be happy with this ;-)  since those should be relatively tiny -- why not to add them somewhere under ```mvpa2/data/cosmomvpa/```?  then provide this code here but we need to figure out how to skip them from tests... may be just indent and use a single ```>``` so doctests module would not even try... I will look into this now