[IMP][MIG] lunch module : migrare to new api and lint a module

[IMP] : use lxml.builder instead of etree.Element , for more code readability
[FIX] : order total is not updated when order line price is change and small code improvements

[IMP] : small code improvments

[IMP] : typos and remove size from field attribute , use TransientModel for wizard

[IMP] : raise exception  when pref_id fails

[IMP]: move can_display_alert to lunch.order and rename it to get_alert_message
[REN] : field active_from to start_hour and active_to to end_hour

[REM] : onchange_price, as total is compute field that is automatically update every time when record is save

[REF] fields view get method