Add l10n_ch_hr_payroll.

Swizerland Payroll Rules for Odoo.

Features list :
* Add Swiss salary rule categories
* Add Swiss salary rules
* Add children in school to employee
* Add LPP range to contract
I'm concerned about this link, this is french only documentation.
The README.rst deserve at least a better english explaination for our neightbour beyond the Röstigraben.