Column Sanity

I think this PR is finally ready to be merged (+/- some things, I'm sure). It's basically an entire rewrite of the `Column` type and everything that entails. The focus for this rewrite was on speed and always forcing columns back to strict/dense version whenever possible.
It would probably be more efficient for you to comment this file before I try and review that it is working the way you probably intend.

Lots of magic numbers, shifty-shifts and andy-ands in there and I'm all like :hurtrealbad: