Add individual financial variables

[nikhilwoodruff]

We need to make sure the CPS dataset includes the data from:

• e00200
• e00900
• pencon

These should be person-level (one variable in place of two _p and _s variables). In taxdata they are tax-unit level, but only refer to one person within that tax unit.

[MarionetteSHF]

#71 #
a simple try, do not mind.