LDEV-3561: Initial implemntation of re-setting read-only flag of Activities on force uncomplete. Each Tools' service has a method to report whether there is significant users' content left it the Activity. If so, it reports the Activity as read-only. Otherwise the flag can be re-set. Grouping, Gate and Complex activities also have their way of checking their immutability.
LDEV-3523: When returning a JSON list of learning designs set design type to "default" if no type exists. Also search on default for designs without a type.