[FIX] Add context propagation for m2m list view

Fix bug https://bugs.launchpad.net/openerp-web/+bug/1279885 :
    Many2many fields in Tree views will not get translated.
    If you check the context for a name_get of a m2m field, it is passed as
    None.

Add context propagation to m2m fields in list views.
Fix translation issues when viewing a a many2many field in a Tree view.
[IMP] website_sale: allow optional products in shop; In shop, it opens the modal jus after having clicked on the 'Add to cart'. The modal contains the optional products.
[IMP] website_sale: Optional product with variant suggestion
[FIX] website_sale: remove disabled attribute on button in the xml template for product without variants
[IMP] website_sale: display 'Product not available' message in product selector
[IMP] website_sale: confirm/options dialog box have same layout of my cart
[MERGE] from master
[IMP] website_sale: optional quantity in product form
[IMP] website_sale: display variants choice in confirm dialog box
[IMP] website_sale: add a tour of test to check confirm dialog box
[FIX] website_sale: add steps to remove the confirm dialog box in tour test
[FIX] website_sale: bind event with touch for ipad
Spawn gevent using same python executable

Solves issues of spawning wrong version of python or popping out of virtualenv
[FIX] website_sale: tour; product split kanban view of product and product template
[FIX] website_sale: tour test customize
[IMP] report intrasat: move field from the view of product product to product template
[FIX] website_sale: rounding price; typo and search sequence of membership
[FIX] membership: remove domain with 'code' filter from the product search view
[FIX] product: remove unused values
[FIX] website_sale: fix keep query and clean code