Import Calculations - Allow user to define which earnings category field is used for calculation.

Currently the import calculations will update Annual pay and hourly rate I believe from pay period salary. Allow the user to define which of these three fields should be calculated upon for the other two fields. (IE client imports annual pay, user could select 'based on' to be Annual Pay, and then hourly rate and per pay period salary will be based on that and annual will not be affected).