only use alpha channel if it exists
[FIX] point_of_sale: fixed rounding issue for pos order when discount added(maintenance: 615322).
[FIX] purchase_requisition: field date_start does not exist on purchase_requisition model so we should not use it in filters

fixes #2838
[FIX] doc: guides section was removed, move CDN to reference
[FIX] ir_qweb: css asset: use which to find lessc and sass

Also, use lessc.cmd instead of lessc on Windows. It allows to run
lessc command with only nodejs and the less module (no cygwin).
[IMP] fields: improve _determine_default() and add test for inherited fields
[FIX] account_asset: moves should use the depreciation line date
[FIX] fix wrong filter in search view (account/sale)

the field section_id is created in addon sale, but used in the account
reporting views.  This commit moves the search view definition
in the correct file.
[IMP] various improvements to the action manager (web client)

* add a replace_breadcrumb option to actionmanager
* correctly calls on_reverse_breadcrumbs when needed
* add a semi-protected way to manipulate breadcrumbs (get_widgets)
* calls do_show when changing widgets
[FIX] web: FieldMany2ManyBinaryMultiFiles must extend ReinitializeFieldMixin

The add attachment button should be displayed while being in edit mode, but not in view mode
As the widget depends on the form actual mode, the widget should be re-rendered each time the actual mode changes

This is the point of the ReinitializeFieldMixin class
[MERGE] forward port of branch 7.0 up to d36c8b5
[MERGE] forward port of branch saas-3 up to 22f2728
[FIX] account_voucher: multicompany compatibility

When the company or the journal is changed, change the period accordingly to make sure to always keep coherant values.
[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
[FIX] fields: fix the translations of the labels of inherited fields
[FIX] models: do not copy translations of fields that are not copied

Fixes #3272.