Boost categorisation analysis markedly.

CategoriationAnalysis can now return full cal/val cat data.
Cal 1990-2008 (even)
Val 1991-2009 (odd)

Categorisation does Quadratic, Linear DA, Stoch. Grad. Descent and
naive cutoff (Decision Tree doesn't seem to work).

New CategorisationChain categoriser that allows chaining of above.