Type subsystem

[lmwnshn]

The type subsystem could probably be cleaned up significantly. Right now, there are a bunch of macros with hardcoded variable names inside them, and a lot of the logic between the different types (e.g. SmallintType vs BigintType) is essentially copy-and-pasted. You could probably replace essentially all the existing type files with a few well-written template functions.

[skyzh]

I think it's time to reduce our type to varchar + integer (maybe decimal, float).