field emplFromDate is forgot in PayHistory entity

A Employment can have multiple PayHistory and should have multiple
because PayHistory should show history of Pay  for a employment  !

Currently, in PayHistory the field fromDate from Employment is confused with fromDate about the current record, it's necessary to have a field emplFromDate (to have the complete employment primaryKey).

Currently user interface for PayHistory is not working, when modifying a PayRecord the current should be expire and a new one should be created.