[FIX] crm, hr_recruitment, task, issue: fixed default priorities + order based on priority (desc for everyone now)

Branch 8.0 is a **stable** branch. This mean no database schema
changes.

violated in _search, do it in SQL to speedup the query. Indeed doing it via search and
browsing the results to validate the various rules is quite costly.

a search_count on mail_message when the actual number of messages or their
ids is not necessary, to speedup the computation.

The field selection menu was not positioned correctly when there was
a long list.  (was not displayed at the position clicked)

Fixes #1719

This reverts commit 4e32b9f6.

8.0 wmsusability jco: Some usabillity issues and a fundamental issue on the location of extra moves

[IMP] Cleaning of reporting (group_by, filters), adding new favourites and default views, some renaming (py and xml files)

+ add meaningful placeholder

(partially revert previous commit)

When a new ir.model.field is created, add the new field in the fields_by_model (cache of custom fields). This is required as the __init__ method would not retrieve the new field if fields_by_model is already set.
Otherwise, the _columns would not contain the new fields and we could not access it without restarting the server (e.g. the installation of a module adds ir.model.fields and use it in the a view.

[IMP] Counterpart locations and weights should not be read-only in case of type service, but should simply be invisible as the other fields

Comparing an id and a browse record will always fail so the exception would have always been raised when changing a model (e.g. updating a module with custom fields).

Merge from nse back-end partial picking wizard

The widget AddToDashboard used to make an ajax call every time the
search view is loaded.  This is often useless and can be annoying when
that request is long.  With this patch, the request is only done when
the user click on the widget AddToDashboard

Fixes #1743, opw 611307