Split of corporate and non-corporate assets for inventories and land

[jdebacker]

B-Tax yield much different ratios than was CBO (2007) finds. In particular, CBO finds:

1. Fraction of land owned by businesses facing corp tax treatment = 46.8% (B-Tax finds about 18%)
2. Fraction of inventories owned by businesses facing corp tax treatment = 72% (B-Tax finds about 60%).

A place to start is in read_bea.py, where these asset types are attributed across industry and tax treatment.

[jdebacker]

With better split to corporate partners, B-Tax now at:

1. 28% for corp land (vs CBO's 47%)
2. 63% for corp inventories (vs CBO's 72%)

Current differences may have to do with different methodologies between CBO and B-Tax for allocating the assets of partnerships to different partner types - in particular, how these are attributed to partners taking net losses.