[16.0][ADD] hr_timesheet_prefill module

[acsonefho]

This module lets the user to create some timesheets (for differents employees/projects/date range) in one shot.

All entry are filled with 0 as unit_amount. But as all entries are generated, the user can now just browse them to fill them with correct time. Without this module, the user who want to create timesheets lines for others employees, have to create them manually and that could take some times.