Fix typo in digits_validation_record error message

issue3824
Improve cache management on access right

issue3848
review5111002
Add tests to float search with None

review4701002
Copy the original field definition

To prevent side-affect with mutable attributes.

issue3814
review4821002
Set relation_field only if there is no ambiguity

issue3899
review6271002
Set relation_field of one2many only when exists

The client use this value if it exists for string concatenation, so having None
fails.
Add MachMixin

issue3867
review5271002
Allow to set a tuple model, dictionary for Reference field

issue3902
review9321002