Lexis coding columns

Depending on the data requested, the following columns should be created:
```
Lexis (AC, or AP in the HMD- they don't have PC explicitly)
Age (bottom)
Year (left)
Cohort (left)
AgeInt (1,5,or10)
YearInt (1,5,or10)
CohInt (1,5,or10)
```
This should cover all cases and eliminate ambiguities. HT Jim Oeppen