OOP demo char + misc

Brought interview type in from oop dataset to look at imputations based
on exit vs core interviews (higher costs exit interviews)
Fixed variable list in initial helper file set up
Fixed month for imputed informal care costs to set to zero when no costs
assigned
Added check to look at missing helper information in helper ds vs adl
impairment direct from interviews
Variable cleaning, set up for demo characteristics
Table of demo char added for 2 and 5year samples
Added imputation table for 5 year lookback (only had 2 year before)