added module hr_worked_days_hourly_rate

This module adds hourly rate and date fields on payslip worked days. Both fields are mandatory only when a number of hours is entered.
I don't agree on every aspect. Hourly rate is standard term in most anglo-saxon countries. What you mean is a factor by which to multiply the rate. Price per hour is not an accurate term and could lead to even more confusion, since you dont buy your employee's services. You pay a salary.

For the ratio, I will add a field to apply a percentage of the regular salary as you suggested.
I will also add a currency field and add help parameters.