BF+RF: "install" all the files from under mvpa2/data

Originally we did not have much of a hierarchy there but now with
openfmri layout it is infeasible to list each by hand.  So I adopted
recursive traversal code and replaced previous explicit subdirectories
specification.  We would just better release

This should resolve problems with "as installed" testing failures
detected on nibotmi boxes, e.g.

http://nipy.bic.berkeley.edu/builders/pymvpa-py2.x-sid-sparc/builds/134/steps/shell_4/logs/stdio