Canada income tax deduction improvement.

Put the field estimated_income field in the hr_deduction_category model instead of hr_employee_deduction.
Also removed the field name in hr_employee_deduction. Added the possibility to have both jurisdiction for a deduction. Example: RRP deduction will always be the same for federal and provincial.

The reason for these changes is to make it more simple for users. I compared odoo with another payroll software and found it easier to understand.

Added unit tests for the sum_deductions method.
Corrected errors in translation files.