The server response to an `onchange` on a one2many is a list of
commands. In case of one2many update (command 1), the server
returns all fields (and not only the modified ones).
When saving the record, this is the client responsability to
specify which fields really changed.
Before this commit, all fields were sent at `write` and not only
the changed ones. This was causing issues when the user couldn't
write on the field ; an error was triggered even though the user
didn't change anything.
To fix this, we only tag as changed (in the datapoint `_changes`
attribute) the fields that have a different value after the onchange.
Martin Geubelle
14cb9af0d6