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
Yes, that's a difference between PyMVPA and CoSMoMVPA. 

In CoSMoMVPA the neighborhood structure (think: QueryEngine instance) defines the .fa and .a for the output. This works nicely for example when running a surface-based searchlight: the input has .fa's 'i', 'j' and 'k' (think: 'voxel_indices') and the output has .fa 'node_indices'. Actually a measure in CoSMoMVPA cannot set .fa, only .sa and .samples. That's a design choice and there may be cases where this is not handy, but so far it seems to work fine for all typical use cases.

Note that the current implementation of CosmoSearchlight actually nukes (removes) any .a's and .fa's present in the output from the searchlight call (i.e. whatever was set by the corresponding measure); only the .fa's and .a's present in the CosmoQueryEngine are set in the output.