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

We could get an js error if the chart contained zero values.

opw-703245

Simplifies the left margin calculation logic with a pre-defined width.
In practice, more use cases should be taken into account, and that could
just make the logic overkill.

opw-697626

In graph view, the y-axis always uses the standard float precision with
2 digits. This might not be enough if the precision was defined
differently for a given float type.

opw-697625

When there are too many labels to display on the x-axis, they overlap
and it simply becomes unreadable. By slightly rotating them, this can be
avoided in most cases.

opw-697625
opw-697626

Since commit 86252428846607cd5f4b18c, the graph view crashed when
displaying a line chart with only one record.  The reason is that the
method display_line can return undefined (if no line chart can be
displayed).  In that case, there is no reasy to try to display its
tooltip.

This commit simply protect against the case where it is undefined.

If the graph view was left while a nvtooltip was shown (thanks to
keyboard shortcuts or during loading time), the nvtooltip remained
and was only destroyed when leaving the action.

Now they are automatically removed with the view as they are now
placed inside of them instead of inside the body element.