Added test code for norbsmall and foveated norb. More on the way.

Datasets remaining to be processed on this thread:
- cos dataset
- MNISTPlus

PS: Need to check cos_dataset. Should it be transferred to create object of DenseDesignMatrix class?

It was complaining a tuple expand error. In some file one line needs 3 elements, but it said only 2 is given. (Just give (48, 48, 1) instead of (48, 48) will fix it, I think.)

Is it better to give the topo_view? By setting topo_view we just set another view of the same data. It does not incur more memory or computation. And the constructor of DenseDesignMatrix will handle all the rest of work for us, including building a view_convertor. But if we call DefaultViewConverter directly, it seems like we intervene into the constructor somehow, which might not be stable between different versions of DensDesignMatrix?