[IMP] point_of_sale: add product variants in reporting

Closes #1322
[FIX] tour.js: wait must be used for the current step instead of the previous step. Remove setimeout delay for activate the element.
Merge pull request #1336 from odoo-dev/master-fix-tour-wait-chm

[FIX] tour.js: wait must be used for the current step instead of the previous step. Remove setimeout delay for activate the element.
[IMP] product : change the constraint while changing UoM of product.