[web test] repair test broken by 0872ac2a1db0 after the above cset, during test instance's url is set before the creation of core entities (ie created at database initialization), hence they have now a valid cwuri.

[dataimport] Drop reference to the 'source' column (closes #4067694). CW 3.19 drops the multi-source support. This column does not exist in 3.19.

[notification] drop on commit sending of message feature of NotificationView It duplicates feature already provided by cw.hooks.notification.notify_on_commit function. Simplify the API on the way.