[FIX] tour.js: introduce common properties selector

Since jquery 1.9, attr selector only matches attributes (the behavior was not
consistent before, sometimes it returned the properties [0]) and tour.js was
relying on those inconsistencies. This commit introduce common properties
selector to allow matching properties during a tour.

[0] http://jquery.com/upgrade-guide/1.9/#attr-versus-prop-
[FIX] website_sale: shop_buy_product: use properties selector
[FIX] website_event_sale: event_buy_tickets: use properties selector