Surgery - updated comments

Updated comments as ran through the code with the revised sample after
fixing the ffs designation variables
SIC - minor comments updates
OOP tables

Added wealth variables at 5 years before death
Added insurance categorical variable looking at self reported insurance
at 5 years  before death
Added medicaid change, wealth variables to quartile output tables
Added a table comparing dementia spending to spending in all other
groups combined
Added quick p=value check to fill in abstract