[Cython] Prototype for parametrized types

[Dag Sverre Seljebotn]

Now that pipeline transforms are in place it is at least theoretically 
possible to take advantage of this:

http://wiki.cython.org/enhancements/typeparameters

Don't apply this to cython-dev just now, it's meant mostly for prototype 
+ if somebody else wants to take over and finish it.

This might mark the end of my coding sprint for now -- I won't break my 
neck by trying to go all the way to numpy arrays right away.

-- 
Dag Sverre