The RPC system was not completely satisfactory, we decided to prepare
the future and do it properly.  This commit introduces the new rpc
system, which replace the previous new one.  We now simply have a
method, this._rpc, which takes a dictionary of parameters.  The idea is
that depending on the parameters, it is able to add correct default
value when necessary.

For situations where we don't have the this._rpc method, we can use the
rpc.query method, which takes the same arguments, but directly calls
ajax.rpc instead of triggering up some events.

* Data manager load_view returns a viewInfo object
* ViewInfo contains: the arch, fields and fieldsInfo objects, and some extra informations
* The fields come from the server and are frozen, without any view attributes (depend of the model).
* The fieldsInfo contains every view attributes and informations.

Applies commit odoo/odoo@dba53fb117d678bf277b55c5a5df83fe44e252fa in the new views.

The import feature was only available in List views before this
commit.

The _rpc method is now the preferred method to do a rpc, so we need to
update all calls.

Use this.rpc instead of Model object, with web.ajax if necessary.

nb: EventDispatcherMixin include now the custom_events managment instead
of widget

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

PURPOSE
=======

Import button in list view only, its confusing for first time user.
When people start using Odoo first thing they try to import contacts or products.

Specificaion
============

Import button should be display in kanban view also

normal mode: Importing only regular/basic fields from source file
advanced mode: Importing any related fields from source file(i.e. if detected pattern in header like '<relational_fieldname>/<fname>')

- Rename following checkbox "Show all fields for completion (advanced)" in "Show fields of relation fields (advanced)"
- If the import file contains a column with a field of a relation field, show the column label in the preview, even if "Show fields of relation fields (advanced)" is not checked > to make it less confusing when importing advanced files (e.g. products with attributes)

After this commit,
 - chinese custom date are supported
 - Possibility to specify the custom datetime format and not only dateformat.
   Withtout it, impossible to import a date column and datetime column at
   sametime with custom format.
 - Add test to check import date with custom format
 - Fix translation where error messages was in the source.

This commit fixes #13783 and closes #13803

Courtesy of @odony for the review ;)