Enforce readonly on WinForm

issue3778
review4511002
Fix set_client of date and time field to convert datetime

issue3795
review4651002
Force Dict client value to be dict

The Dict widget requires that get_client returns a dict.

issue3796
review4671002
Fix Form set_cursor when cursor widget doesn't exist

issue3798
review4711002
Set value for constraining domain of non-relation field

The validation method should also set value for the local domain like it does
for the inverted.

issue3794
review4641002
Fix uninitialized focus_widget case in Form.set_cursor
Don't update completion if entry is no more displayed
Tryton client es_CO translation
Validate field on simplified domain

issue3823
review4871003
Let cancel button of window form for reaonly screen

issue3826
review4891002
Fix invalid inversion domain to use None instead of False

issue3681
review4891004
Ensure ViewSearch.searches has always the right type

issue3828
review4941002
Make button reload all parents

issue3815
review4841002