[FIX] calendar: gantt view argument

There is no 'date' field.
Fixes #3496
[IMP] point_of_sale: add a zero default margin when printing a receipt from the browser.
[FIX] web: many2many_binary widget upload

once widget extended with ReinitializeFieldMixin, the event binding with the binary file input and the on_file_change method can be done in initialize_content instead of start

This fix is related to d36c8b5c9bf7ab9215bc63db6ee49bec5e5b225b
[MERGE] forward port of branch 7.0 up to ae99a93
[MERGE] forward port of branch saas-3 up to c8df9fc
Merge branch '8.0' of https://github.com/odoo/odoo into 8.0-linux64