[WIP] <sale_order_line_dates> extending standar <sale_order_dates>

Este modulo pretende realizar lo mismo que sale_delivery_date (https://github.com/odoomrp/odoomrp-wip/tree/8.0/sale_delivery_date), pero usando el modulo del estándar de odoo sale_order_dates, comentado por @clonedagain en el issue #219 
It is a WIP, I have to change an onchange, but it is a mix between new and old api, and I do not have very clear how to do.
I have uploaded so that @pedrobaeza can point me in the right direction :wink: 

The onchange will be, if sale.order requested date is changed, put the same in all sale.order.lines