With the new views, the barcode mechanisms were completely broken,
because the view and widget JS code was totally changed.

This commit update and refactor all that code to make it work with the
new design philosophy.  Also, it update the coding style.

This commit introduce a full redesign of all JS views.  We started
basically from scratch.  The goal was to unify all the various views
under a common framework, to make them testable, to make then usable in
different conditions (in studio, or in the frontend), and to make our
lives easier.

Some important points are:
- we introduced new coding guidelines (camelCase, 80 chars width, ...)
- we have a brand new testing framework (still QUnit based)
- kanban view moved to the web addon
- calendar view (formerly web_calender) moved to web as well
- the tree view was removed
- all new code should be documented

We hope that this code is the start of a new era for the Odoo web
client, we want to have a high quality codebase, well documented, well
tested, well designed.

Work done by the framework team: mostly aab, ged, chm, dmo, qsm

In some cases, several barcode widgets can be found on the same page.
This is for example the case of the stock picking: there is a widget on
the `stock.picking` model (main view) itself, and a widget on the
`stock.pack.operation` model (modal view).

In this case, when the focus is not set directly on the field which
needs to be filled in, both widgets will trigger a `barcode_scanned`
scanned event. This will call the `on_barcode_scanned` Python method
which can lead to errors/warning. For example, the `on_barcode_scanned`
method on the `stock.picking` model raises a warning in case the barcode
scanned does not match any product/package.

The fix is to make sure that the event target is located in the correct
DOM element.

opw-677506

Only the barcode handlers in the front view should listen to barcode events.