Define BASE_URL and DATA_URL js variables in the login template. Closes #13385185
Those are expected to be defined in almost every js files. They were not before
this patch because login form doesn't use the regular main template.
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')