Remove old datasets.

Datasets will be migrated to a new structure. The new dataset object
is described here [1].

Old datasets where deleted so that the package could be included in
Debian (license and package dependencies issues)

[1] http://sourceforge.net/apps/trac/scikit-learn/wiki/DatasetProposal

From: Fabian Pedregosa <fabian.pedregosa@inria.fr>

git-svn-id: https://scikit-learn.svn.sourceforge.net/svnroot/scikit-learn/trunk@616 22fbfee3-77ab-4535-9bad-27d1bd3bc7d8