[web/data] fix treeview regression (closes #3526466)
Changeset 68cde7431c2c "[js] remove 3.9 bw compat (where apparently
unused)" removed the use of form.callback from loadxhtml, which treeview
relied on. Update to add a callback on the loadxhtml return value
instead.
change_attribute_type('CWCache', 'timestamp', 'TZDatetime')
change_attribute_type('CWUser', 'last_login_time', 'TZDatetime')
change_attribute_type('CWSource', 'latest_retrieval', 'TZDatetime')
drop_attribute('CWSource', 'synchronizing')
add_attribute('CWSource', 'in_synchronization')